How do I replace water line from copper to pvc for faucet hook up?

Are you saying that all that comes out of the wall is a copper pipe? There should be a angle stop (see image) on the end of that \copper pipe. Is the copper pipe capped off? More details please. Tom

Cooper pipe came up through floor, I have put on transition union and have copper pipe from pvc to faucet. I now have pin hole in copper on elbow. I want to take pvc up to a 90 elbow and hook up to flexible faucet hose.

If I understand you correctly you're asking how to convert from copper to PVc. Correct? Purchase a Sharkbite male adapter in the correct size.)1/2"?) and as PVC female adapter along with small cans of PVC primmer and cement. Does that answer your question? Tom

Some what. It is a 1/2" water supply to kitchen faucet, but the flexible line to the faucet itself is smaller with a metal nut. I can't hook metal to pvc fitting, correct?

The you install a inline compression stop on the raiser. The small metal nut will connect to the outlet. Good luck. Tom

I also recommend a Sharkbite adapter for attaching to the copper. They take only a moment to install and the four I used recently never leaked a single drop.
Skip the PVC and run your flexible hose right to the Sharkbite. When I replaced faucets in our master bathroom I used 1/2" to 3/8" Sharkbite 1/4 Turn Angle Valves and flexible hoses with 3/8" on one end and 1/2" on the other (1/2" goes to faucet). Quick, easy (no cursing from me!), and as I said before, not a drop.
(BTW, I'm not an expert. I'm just a guy who haunts this forum for help.)