You can find the volume of a cylinder by mulitplying the squared radius of the cylinder by pi and the height of the cylinder.
For instance, if the radius of my cylinder was 5, and the height of the cylinder was 20, then to find the volume of the cylinder I would do the following:
5 x 5 x 3.14 x 20 =
In this case, the volume of the cylinder would be 1570 cubed units.