Homework Help: Gravitational PE, Elastic PE

i need help with this problem. i have no idea how to do this.

A 1.41 kg object is held 1.38 m above a relaxed, massless vertical spring with a force constant of 288 N/m. The object is dropped onto the spring.
(a) How far does the object compress the spring?
1 m

(b) Repeat part (a), but now assume that a constant air-resistance force of 0.872 N acts on the object during its motion.
2 m

(c) How far does the object compress the spring if the same experiment is performed on the moon, where g = 1.63 m/s2 and air resistance is neglected?
3 m

 

i didn't put those answer. i really don't know how to do this problem or where to start