You could try to manually remove the shell by gently inserting your finger and try to find the entrance to her oviduct. Once in, manually remove the shell.
it is definitely a hard shell, I can feel the broken shell in her abdomen. I already checked the feed store, and they don’t have the Amoxicillin.. no tractor supply

I agree with Kathy, if you can feel a hard shell and you don't have vet care, then manually removing the shell is your best option.
Do you have a parent, neighbor or friend that can help you with this? Extra hands would be good.
OK and don't worry about the medication right now. Trying to get the egg out is what you will want to do.