Read the label on the trailer power cord or electrical panel before buying an EMS.
READING GUIDERV ELECTRICAL BASICS
30A vs 50A RV Electrical Service
Understand what 30-amp and 50-amp service change about campsite hookups, adapters, EMS selection and usable power.
A 30A RV has one 120V hot leg and substantially less available power than a 50A RV, which uses two 120V hot legs. The safest buying rule is to match electrical protection and primary hookup gear to the trailer service you actually have.
What matters in practice
Adapters can change plug compatibility, but they do not magically give the trailer more electrical capacity.
High-draw appliances used together are more likely to trip limits on 30A service.