This is my preamble
\documentclass[9pt]{beamer}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{lmodern}
\usetheme{Goettingen}
\usecolortheme{whale}
\usepackage{verbatim}
And this is the bibliography
\begin{frame}{\LARGE References}
\begin{thebibliography}{9}
\bibitem{S1}
\small{Source 1}
\bibitem{S2}
\small{Source 2}
\bibitem{S3}
\small{Source 3}
\bibitem{S4}
\small{Source 4}
\bibitem{S5}
\small{Source 5}
\bibitem{S6}
\small{Source 6}
\end{thebibliography}
\end{frame}
In the slide it displays like this

However I couldn't figure out how to display numbers instead of this paper symbol. Any help is appreciated.
\setbeamertemplate{bibliography item}{\insertbiblabel}should help. – leandriis Oct 24 '21 at 11:54