The best option is get an adapter from evseadapters.com to plug directly into the UMC.
Second best would be an adapter from those to a 14-50R and use your tesla 14-50P adapter. Just be sure if you do that with the 30 amp outlet you dial back the amperage in the car, although that’s not ideal to rely on for long term as there’s always a chance the software limit gets reset unintentionally and it tries to pull more than 30 amps.