[81MC]

I literally just went through some fiasco with valves

Remove that chrome trim ring and sleeve. If it’s a new enough Moen to work with their current products (Posi-temp) it’ll slide off. Yours looks like it maybe threads on?

Make sure the water is turned off.
Remove the cartridge retaining clip.
Remove cartridge - it’ll probably really not want to come out. They make pullers, but some vice grips and patience with some flat head screw drivers, cognizant of the old plastic bits, it’ll come out.

If the valve doesn’t identify itself, take it to a plumbing supply, or even HD and compare.

Your water lines look taped and threaded, not soldered? For some reason I’m thinking it’s a delta?

Worst case, but one of each from the cheapie fixit section from Hell’s Depot and see what fits.

If you do change the valve, because, let’s say your significant other changes her mind in where she wants the valve to go after paying a plumber to move the spout and after drywall is up...pex is like adult lego and soldering is a skill Everyman should have.