i have a 1995 GM 6 Cylinder Step-side pickup. I checked the fuses and bulbs but the rear lights do not work

Check the ground wires under the bed. They catch a lot of road salt and water and they start to corrode. Follow the wiring harness from the taillight back until you find them.

l had the same problem, broken wires drivers side, half way to 3/4 down the bed, wireing harness should be easly visable.

If it is used and new to you.check to see if they had a tow package connected. Sometimes people hook those up without a harness and just rip them out when they sale them. otherwise, l figure something may have cut your main power relay to the rear light power coupling