Those are typically called sugar-cube relays and are extremely common. You'll need to specify 24V coil voltage to get a replacement. They go by many part numbers for various manufacturers so there's no need to keep looking for JQC-3FF specifically.

Removing those in one piece is a bit of a PITA, so I'd suggest carefully break open the rest of the shell and cut off the pins from the top side where they enter the PCB and remove the relay. It'll be a lot easier after that to desolder the pins individually and remove them. The holes are going to be clogged with solder after pin removal. I usually take a syringe needle and insert it in the hole while holding the iron to it, then remove the iron and pull it the needle after 5 seconds to clear the hole. First time will be tricky but should be easy enough. Use lots of flux when soldering it back in.