Hard to tell from your description, but if the hole your derailleur mounting screw threads into is stripped, it can be repaired with one of these:
https://wheelsmfg.com/ds-1.html
If you have a removable hanger whose mounting holes are stripped you can repair the holes with a Helicoil, tap it out to a larger size,and use a a bigger screw or use a jam nut behind the dropout and a short screw to mount it if there is room.
If you upload some photos to a photo-sharing site and post a link we might be able to help you better.