Do you need a state ID to get the piercing done? If we need one but don’t have and is 18 can we use our passports as a substitute for it?

State issued ID or passport are acceptable.

You don't need state ID. Any international id is fine, passport is definitely the best. I used my international driver license.

Passports are generally an accepted form of ID, try to call and ask to be sure though but I'd be surprised if they didn't