Originally Posted by CO_Hoya

If the OPs bike matches the 1995 Trek catalog, it will be a equipped with a 3x7 drivetrain (Shimano Alivio/STX) as OEM. As per Hondo6 above, it would be a good idea to confirm the size of the freehub before making a purchase.

If the OP can post some pictures of the bike, especially the rear hub and cassette with spacing and any part numbers visible, I'm sure someone here will be able to assist with sorting out what's compatible.

That's a nice enough frameset that putting some money into a new drivetrain can be worthwhile. Shimano's Altus line looks like it has 7-sp offerings as well if you do have the smaller freehub.

While I have no personal experience, I hear that Microshift components are of good quality and it looks like they have a 7-sp MTB group ("Mezzo") that may be worth tracking down for comparison shopping.