The question "how much space is inside a solid?" is actually asking about the volume of that solid.
The volume of a cone is given by
[tex] V = \dfrac{1}{3}\pi hr^2 [/tex]
where h is the height of the cone, and r is its radius.
So, you only need to plug in the values:
[tex] V = \dfrac{1}{3}\pi\cdot 50 \cdot 200^2 = \dfrac{2000000\pi}{3}m^3 [/tex]
