Craig, welcome to the Tesla community. What you want is the J1772 adapter for using generic Level 2 charging stations. It's available at Tesla.com/shop/charging/adapters, for $55. It comes with the car, so the person you bought from owes you one!
It's important to get the terminology correct. This is not a "Supercharger adapter". There's Level 1 charging (any outlet, 120 volts/15 amps, about 5 miles of range per hour of charging), Level 2 charging (240 volt, 30 to 70 amps, 30 to 70 miles of range per hours - depends on the charger in your car, Teslas max out at 48 amps, and if you're using the Mobile Connector Kit (also available at Tesla.com, and recommended to carry with you) it's limited to 32 amps), Level 3 charging, also known as Direct Current Fast Charging (DCFC) or Direct Current Quick Charging (DCQC) (400+ volts and output measured in kilowatts (kW) of 50 to 350kW, 150 to over 1,000 miles of range per hour, depending on what the station can provide and what your car can accept. "Superchargers" are at the high end of Level 3 charging. Hope this helps. "EV grin"!