You should first sketch to see how your body looks like. if you want you can use some of the following programms: Matlab, Mathematica, Matcad, or their free alternatives: wolframalpha, octave.
I can't show you the graph should look like because the graphing tool does not allow 3D graphs.
Now to calculate volume of the solid, you use the following formula:
`V=int int_S f(x,y)dxdy` where `S` is the area under parabolic cylinder and `f(x,y)=z`.
Hence we haave:
`V=int_0^3dx int_0^2 (4-y^2)dy=int_0^3(8-8/3)dx=int_0^3 16/3dx=16`
Hope this helpes