Question

Charge Q=4 micro-coulombs is distributed uniformly over the volume of an insulating sphere of radius R=.05 meters. What is the potential difference between the center of the sphere and the surface of the sphere?
How do I approach this problem? I tried integrating dV=-Edr from r=infinity (V=0) to r=.05 but didn't get the right answer. Should I be integrating with respect to the volume?... the text book said the answer was 360 kV.