Go in your My Tesla page and click on view specs for the car you ordered, then copy/paste the URL of the spec sheet on a word page and within the URL you will find the code for your charger:
CH05 48Amps
CH04 72Amps
Normally you shouldn't have ordered the upgrade since it's not available in the configurator for a 75, you would only be able to have your SvC upgrade your car to high Amp charger once they get the car. It's a upgrade they can do at the SvC.