car wont start alternator belt 88 gti

i was driving my 88 gti and stalled and it wont start i looked at the alternator and the belt is gone so could that be why the batery doesnt have enough power to start the car i bought a new battery and that didnt do anything so i am pretty sure that it is a belt

is it cranking over at all. cause if u bought a new battery it should still start and run