How do you tell if the transmission needs to be replaced or if it's the clutch in a 1995 Plymouth Neon?

well if you put the car in any gear and let out the clutch if you rev the engine and it dosent move or moves a little then it's the clutch but if it's a grinding noise and it doesnt move at all i'd say its the transmission my car was grinding and not moving and it was cause the spider gears were all busted and i had to rebuild my transmission