A prism is a 3D shape will all identical cross-sections.

A cylinder is a prism with circular cross-sections.

The volume of a prism is the cross-sectional area X height of the prism (in other words, the number of cubes in one layer - which is numerically the same as the cross-sectional area, times the number of layers - which is numerically the same as the height of the prism).

Go from here.