Create a 6 vertex circle, right click and subdivide (all the parameters are in the Operator box on the bottom left of your 3D view):

Extrude inwards (press EEnter then Scale with S) and make the edge loop a circle with the LoopTools addon (activate the addon and right click > LoopTools > Circle):

Activate the Auto Merge and Snap to Vertex options, duplicate your mesh and stick the duplications:


Extrude downwards (E and move the selection along the normals), in Object mode right click > Shade Smooth and in the Object Data panel > Normals, enable the Auto Smooth option:
