Good Morning @nano.7az83u,
All phones purchased from Republic, by design, ship with a SIM preinstalled. If the Moto Z was purchased from a third party, a SIM, if needed, must be acquired separately.
Our apologies for any confusion as this is not universal advice. Some but not all active SIMs move from phone to phone. It depends entirely on the brand, model and generation of the phone whose SIM one wishes to move.
Based on this alone, you will need a new SIM for the Moto Z you purchased. As you may know, Republic offers multiple coverage options for its newer compatible phones. To be certain we point you to a SIM with the best coverage for your area, might we trouble you for a zip code (nothing more)?
It would also help us better help you if we knew the generation of the Moto Z involved. Republic supports the Moto Z, Moto Z Play, Moto Z2 Play, Moto Z3 Play and Moto Z4. Do you know which of those you purchased?