First you should know the value of the radius which based on the picture is 9 in, next step is multiply 9 two times itself, then after that multiply it with the equivalent of pi which is 3.14 once you get the answer multiply it once again with the height of the cylinder The following information I've stated is derived from the formula
Pi (sorry I don't have the proper sign) multiplied to the radius then multiplied to the height of the cylinder
Once you've encounter a problem in which the radius isn't stated simple divide the diameter by two and you're good to go
Calculate the area of the base (which is a circle) by using the equation πr² where r is the radius of the circle. Then, multiply the area of the base by the height of the cylinder to find the volume.