Welcome to Beoworld !
I agree completely with Solderon29.
There are a total of three belts in the tapedeck (plus one for the drawer). If one belt is bad, the others will be too.
Belt kits for this model are readily available (from me) and mounting instructions with photos etc. can be included.
I've heard of Turntable Basics. Are you sure that the belt you ordered are for a BeoCORD 5000, not a BeoGRAM (turntable) ?
I ask because they list no less than 3 different sizes for the same turntable deck, (none the correct size BTW).
I know they are listing belts also for the Beocord 8000 (not the correct sizes either) but I don't see the Beocord 5000 anywhere.
Martin