The screws thread through the lenses into the light buckets which mount to tabs in the license plate bezel. You can find both the lenses and buckets in junkyards if you are willing to do the work to retrieve them; however these are often cracked and broken too. Attached are the part numbers I could easily find for my 99's license plate lights/lenses etc.
When you do disassemble the lights to replace the bulbs, be careful, the plastic of the license plate bezel will be brittle, and if they break or crack (which is common) they are easy to fix with the right epoxy; just like the lock cylinder mounting screw bosses.
Remove the bezel (lots of write ups on that) and try to catch any broken plastic pieces. Epoxy the broken pieces, filling the screw holes, and let dry for a few days. You can drive without the bezel in place, just tape over the holes in the hatch and screw your license plate back on. When the epoxy dries, drill holes in the repaired screw bosses smaller than the screws and thread the screws back in.
Pro Tip: reinforce all the screw bosses on the underside of the plate bezel (from the inside) with epoxy and upgrade to SS screws :yo: