NEMA 5-15 Plug, Household regular 3-prong 15A 125V male. NEMA 14-50 Receptacle, 4-prong female for Electrical Car charger, right-angle type, with handle and neon-light. Electrical Vehicle adapter cord, for EV charger with 14-50 plug, want to plugin a regular 15A 3-prong 120V NEMA 5-15 socket. Molded connector with STW 10AWG/3C cable, support max 30 AMP loading. Pins and terminals are made with nickel-plated brass to prevent oxidation rust. Length : 1.5 Feet, 3 Feet or 10 Feet NEMA 5-15P to 14-50R for EV Charging, Maximum operationg power of 20 Amp, 125-Volt, 2,500-Watts.

EV Charging requires high current for an extended time, it is a continuous load and it must be limited to 80% breaker capacity. Please follow the 80% rules, if your circuit breaker is 20 Amp, please limit the amperage manually to 16 Amp.
If you want to use your Tesla UMC charger with 14-50 adapter plug into 5-15 household regular 15A 120V outlet.
This adapter cord can help you to do it.