If you managed to save them, they would probably need to be a house chicken only, I suspect they may get bullied to death by other chickens even if they could get around the coop and run alright.
They would certainly need a higher level of dedication and care that you may not be prepared to handle.
I don't intend to discourage you from trying to save them, and I'd likely try to do the same, but you need to be aware that it's unlikely this chicken will be able to live a "normal" chicken life and will need a much higher level of care.
If that's something you're prepared to provide, I'd definitely recommend a vet if available. It'll give them the greatest chance for survival.
Even with a vet's care, chickens can be delicate, and they might not make it.
If a vet isn't available, and you're still sure you want to try, you'll need to make sure that the leg was removed cleanly at a joint. If it has a partial bone, that will get infected and kill the chick. If you can't cleanly amputate yourself and can't take it to a vet, you won't have much choice but to cull.
If it's a clean amputation, disinfect and dress the wound. Personally I'd prop them up in a harness in a little cup like some people do to treat splay legs to keep them off the wound and putting weight on their good leg. They'll been to be hand fed and kept away from the other chicks. Monitor and hope for the best.
