if the circuit not noted as to what it covers on the panel you will have to disconnect Every Thing powered by 120 volts in the trailer. The convertor, the frig, the microwave, the TV, the hot water heater if it has an electric element, and anything else that is so powered.
Once all are disconnected attempt to turn on the breaker. If it still blows it could be a failed breaker, replace and try again. If it still blows there is a shorted wire somewhere in the trailer, not that likely, or something 120 volts is still connected, more likely. If it holds reconnect, one at a time all those items you disconnected. If the breaker blows it problem is with the last item you plugged in.
WBCCI 12156 AIR 3144 WACHUNG TAC NJ6
2004 Excursion 4x4
1991 34 ft. Excella +220,000 miles, new laminated flooring, new upholstery, new 3200 lbs axles