As Bill Kapaun said, the first thing you should do is to measure the rear drop out spacing. If it’s 126mm then you want to look for a 126mm rear hub:
1. Some of these are freewheel hubs. They are not as strong as cassette hubs but if you are not too heavy a rider a freewheel hub will work fine. If you are lucky you might find Phil Wood or Mavic freewheel hubs which are much stronger.
2. You might come across a Suntour or Helicomatic cassette hubs-avoid these.
3. The best case scenario would a 7 speed Shimano HG hub in 126mm width.
4. The next best case scenario would be a Shimano 130mm HG 8-10 speed hub. In most instances you can swap the freehub body and narrow these down to 126mm.