When I pedal the rear wheel is not turning
This sounds like either the freehub on the rear wheel, if you have the newer cassette style, or the freewheel, if you have the older thread on design, needs to be replaced.

These parts contain the pawls which drive the wheel forward when you pedal. If the pawls are broken, or simply not engaging the hub shell, you will pedal with no forward movement.

See this answer to the question What causes the noise that race wheels make when you are not pedaling?