Tesla no longer fit custom plates, unless you're trading in a vehicle with one and they need to swap between the two vehicles.
So you'll need to organise to swap the plate yourself, either via a phone call or in person at a licensing centre - depending on how it works in your state.
in NSW and VIC you can ask Tesla to fit the cheaper fullsize plate on the car, instead of the more expensive slimline they put on by default.
That way you're not wasting money on a plate you'll remove anyway.
In WA they only ever put the ugly fullsize plate on, I don't know about other states.