Changing the position of a plot in tikzpicture and its caption

Question

I want to achieve the following. Reference figure is attached.

1. In figure 16.1, print 1% in the same way as highlighted in red in the attached figure.
2. Move figure 6.4 to the left (under figure 16.1).
3. Add caption to the right of the figure 6.4 (space pointed by red box in the attached figure).

Following is my code

\documentclass[acmsmall]{acmart}
\acmJournal{CSUR}
\usepackage{pgf-pie, etoolbox} 
\usetikzlibrary{shadows}
 \usepackage{color,soul}
 \usepackage{tikz,pgfplots,pgfplotstable}
 \definecolor{cadmiumorange}{rgb}{0.93, 0.53, 0.18}
\begin{document}
\begin{figure}[h]
\centering
\captionsetup{justification=centering}
\begin{tikzpicture}
[
every node/.style={align=center},
pin distance=9mm,
font={\scriptsize},
scale=0.55
]
%   \pie [text=legend]{
\pie [polar, explode=.1]{
    1/2222,
    9/2222,
    20/2222,
    17/2222,
    24/2222,
    29/2222}
\node (O) at (2,-3.7){(16.1)};
\end{tikzpicture}
\begin{tikzpicture}
[
every node/.style={align=center},
pin distance=9mm,
font={\scriptsize},
scale=0.55
]
%   \pie [text=legend]{
\pie [polar, explode=.1]{
    63/Ccccccccccc,
    30/Rrrrrrrr,
    3/Tttttt,
    4/Ooooo}
\node (O) at (0,-3.7){(16.2)};
\end{tikzpicture}
\begin{tikzpicture}
[
every node/.style={align=center},
pin distance=9mm,
font={\scriptsize},
scale=0.55
]
%   \pie [text=legend]{
\pie [polar, explode=.1]{
    52/Aaaaaaaa,
    17/Iiiiiiii,
    31/Coooooooooooo}

\node (O) at (0,-3.7){(16.3)};
\end{tikzpicture}

\begin{tikzpicture}
[
%scale =.5, 
%transform shape,
font={\large},
scale=.5
]
\begin{axis} [
xtick={2016, 2017, 2018, 2019, 2020, 2021},
major x tick style = transparent,
ybar = 2\pgflinewidth,
bar width=5pt,
%   ymajorgrids = true,
ylabel={Number of Stocks},

symbolic x coords={2016, 2017, 2018, 2019, 2020, 2021},
scaled y ticks = false,
%   enlarge x limits=0.35,
ymin=0,
minor y tick num=5, 
xlabel style={yshift=-.3cm},
ylabel style={yshift=-.5cm},
tick label style={font=\large},
legend style={at={(.5,-0.1)}, anchor=north, /tikz/every even column/.append style={column sep=.2cm}},
legend columns = -1

]
\addplot[red!20!black,fill=blue] coordinates {

    (2016, 1) 
    (2017, 6) 
    (2018, 10)
    (2019, 5)
    (2020, 11)
    (2021, 11)
};
\addplot[red!20!black,fill=yellow] coordinates {

    (2016, 0) 
    (2017, 0) 
    (2018, 3)
    (2019, 4)
    (2020, 6)
    (2021, 8)
};
\addplot [red!20!black,fill=cadmiumorange] coordinates  {

    (2016, 0) 
    (2017, 0) 
    (2018, 0)
    (2019, 1)
    (2020, 0)
    (2021, 1)
};
\addplot [red!20!black,fill=cyan] coordinates {
    (2016, 0) 
    (2017, 0) 
    (2018, 1)
    (2019, 2)
    (2020, 0)
    (2021, 0)
};
\legend{Firm1, Firm2, Firm3, Firm4}
\end{axis}
\node (O) at (3.5,-1.7){\scriptsize(6.4)};
\end{tikzpicture}
\caption{Quantitative analysis of research methodology showing various distributions.}
\label{fig:6}
\end{figure*}

\end{document}

Answer 1

I mentioned in my comment as to how to achieve point #1 of the OP's request. For points 2 & 3, the following code achieves it:

1. See comment to OP's question (approximated here)

2. judicious use of \hfill to overcome \centering

3. place the \caption in a minipage

In general asking a question with a single point, rather than 3 separate issues, is more likely to generate a response.

Here is the code:

\documentclass[acmsmall]{acmart}
\acmJournal{CSUR}
\usepackage{pgf-pie, etoolbox} 
\usetikzlibrary{shadows}
 \usepackage{color,soul}
 \usepackage{tikz,pgfplots,pgfplotstable}
 \definecolor{cadmiumorange}{rgb}{0.93, 0.53, 0.18}
\begin{document}
\begin{figure}[h]
\centering
\captionsetup{justification=centering}
\begin{tikzpicture}
[
every node/.style={align=center},
pin distance=9mm,
font={\scriptsize},
scale=0.55
]
%   \pie [text=legend]{
\pie [polar, explode=.1]{
    1/!1%~~2222,
    9/2222,
    20/2222,
    17/2222,
    24/2222,
    29/2222}
\pie [sum=6, hide number,explode=.1,radius=.55]{1/}
\node (O) at (2,-3.7){(16.1)};
\end{tikzpicture}
\begin{tikzpicture}
[
every node/.style={align=center},
pin distance=9mm,
font={\scriptsize},
scale=0.55
]
%   \pie [text=legend]{
\pie [polar, explode=.1]{
    63/Ccccccccccc,
    30/Rrrrrrrr,
    3/Tttttt,
    4/Ooooo}
\node (O) at (0,-3.7){(16.2)};
\end{tikzpicture}
\begin{tikzpicture}
[
every node/.style={align=center},
pin distance=9mm,
font={\scriptsize},
scale=0.55
]
%   \pie [text=legend]{
\pie [polar, explode=.1]{
    52/Aaaaaaaa,
    17/Iiiiiiii,
    31/Coooooooooooo}

\node (O) at (0,-3.7){(16.3)};
\end{tikzpicture}

\begin{tikzpicture}
[
%scale =.5, 
%transform shape,
font={\large},
scale=.5
]
\begin{axis} [
xtick={2016, 2017, 2018, 2019, 2020, 2021},
major x tick style = transparent,
ybar = 2\pgflinewidth,
bar width=5pt,
%   ymajorgrids = true,
ylabel={Number of Stocks},

symbolic x coords={2016, 2017, 2018, 2019, 2020, 2021},
scaled y ticks = false,
%   enlarge x limits=0.35,
ymin=0,
minor y tick num=5, 
xlabel style={yshift=-.3cm},
ylabel style={yshift=-.5cm},
tick label style={font=\large},
legend style={at={(.5,-0.1)}, anchor=north, /tikz/every even column/.append style={column sep=.2cm}},
legend columns = -1

]
\addplot[red!20!black,fill=blue] coordinates {

    (2016, 1) 
    (2017, 6) 
    (2018, 10)
    (2019, 5)
    (2020, 11)
    (2021, 11)
};
\addplot[red!20!black,fill=yellow] coordinates {

    (2016, 0) 
    (2017, 0) 
    (2018, 3)
    (2019, 4)
    (2020, 6)
    (2021, 8)
};
\addplot [red!20!black,fill=cadmiumorange] coordinates  {

    (2016, 0) 
    (2017, 0) 
    (2018, 0)
    (2019, 1)
    (2020, 0)
    (2021, 1)
};
\addplot [red!20!black,fill=cyan] coordinates {
    (2016, 0) 
    (2017, 0) 
    (2018, 1)
    (2019, 2)
    (2020, 0)
    (2021, 0)
};
\legend{Firm1, Firm2, Firm3, Firm4}
\end{axis}
\node (O) at (3.5,-1.7){\scriptsize(6.4)};
\end{tikzpicture}\hfill\hbox{}
\begin{minipage}[b]{.6\textwidth}
\caption{Quantitative analysis of research methodology showing various distributions.}
\label{fig:6}
\vspace{50pt}
\end{minipage}
\end{figure*}
Following text
\end{document}