My motorhome, and both previous trailers that I owned, had a power cord inside a compartment. This power cord has a
30 Amp plug on it. You will need an adapter to plug this into a home power receptacle (shore power). Do NOT use a power cord with 2 male connectors to power the trailer. You may have some other power connecter that requires an adapter of some sort.
The converter is an electrical box that converts the 120vac power to 12vdc that charges the battery and supplies 12 volt power to the lights and other 12 volt things in the trailer when you are plugged into shore power.