The volume of the cylinder would be 128π in^3
Finding the volume of a cylinder involves its formula: b*h=v. In the case of a cylinder and even cones, your base is a circle, and therefore is the area of said circle.
What you first want to do is find the area of the circle, to do that you need to know the formula which is r^2*pi. A cylinder has two congruent sides which are the circles, therefore the radius of one circle is the same as the other. Now use the radius of the circle on the top of the cylinder and square it. 4^2=16. Next we need to multiply 16 by pi (pi can be multiplied like a variable and just added next to 16. Therefore 16*pi= 16π.
Next now that you have your base (16π) you must multiply by your height which is 8 in this case (the length between the two circles). 16π*8 and now multiply as it it were two terms (a variable and whole number) so 16π*8= 128π
