How do I do 1, 2, and 3?

QUESTIONS: Assume Earth is a giant conducting sphere with a radius of 6.37 x 10 m. Of course, you might ask "how did it get that way?" Quiet. We don't talk about that. Now assume that a total of +1000 C of charge has been uniformly distributed over Earth's surface. Determine the potential differences between... 1. Infinity and the distance of the Moon's orbit (3.84 x 108 m from Earth)... 2. The Moon's orbit and the surface of Earth. 3. The surface of Earth and the center of Earth