convert drum to disk brakes
 

I have a good understanding about cars in general but not so much in mechanics. I had a friend come up to me asking if it was possible to change is drum breaks to disk on his 2009 volkswagen jetta.

of course its possible - but doesnt make any sense :bonk:
a jetta needs no brakes on the rear :D

Your friend's best bet is to get the rear uprights/hubs/discs/calipers etc. from a Jetta of the same generation with rear discs (if there was an option to get them from the factory, or maybe from a GLI or something).