Just bought a 1995 toyota camry and can't get the old plates off. Have used wd40 and vice grips. One screw will turn but not come out , can't move the other ones.

Cut off with hani grinder, nut cutter to cut the old nut off, drill the screw out.

Have you checked the back side and made sure that is not just turning back there.

Try applying PB Blaster, Kroil, liquid wrench, or other suitable penetrant. Allow to soak for several minutes and the parts should come apart.

Hi Kim. I assume you're talking about the back plate. Behind the plate are what we call nutserts. They pinch onto the molded plastic bumpers with a threaded hole in the middle. The screw you have has seized to the nutsert and become one. As said above, a grinding tool is best bet. A lot of households have smaller dremel grinders with little diamond blades on them. That would work, but very time consuming.
Can you stop by a shop and ask one of the nice guys to do this for you? Sure you can. Go for it. Save yourself the trouble.