In order to find the volume of a cylinder you need to know either the radius of the cylinder or the diameter. You gave the radius, but if you had the diameter, you could reduce that number by half to get the radius.
The formula for finding the volume of a cylinder is:
You can use the "pie" button on your calculator or us the standard 3.14. "r" is the radius squared and "h" is the height.
v = 3.14(2^2)8
v = 3.14 x 4 x 8
v = 100.48
The only problem that I see with that answer is that it is unitless. The problem did not specify if the radius and height were in cm, m, inches, or feet. It's possible that your cylinder is 100.48 cubic cm or 100.48 cubic meters. The number of the answer is the same, but the difference in volumes would be enormous.