are you saying that i should cut the copper pipe and unscrew the adapters and save them for the new vavle?
I think most of the plumbers have mentioned cutting the copper pipe.
If you buy a threaded ball valve, you can get by with one coupling, saving the current male adapter that is now on the copper.
Cutting the copper about 6" away and saving the section.
You can then thread that to the new valve, and the valve onto the existing threaded nipple.
Then you will be left with the coupling to connecto it together again.
You can solder the coupling,
Or use a fitting like a sharkbite.
The threaded ball valve where it threads onto the tapered threads will need a pipe thread sealant, either Teflon Tape, or Pipe Dope (thread sealant in a can)