You would have to go back to early 1970s, possibly 1960s to find trailers that did not have a"converter/charger"..
Time to do a deep search following the wiring up to the tongue.
You most certainly should have a converter unless a previous owner removed it.
Is one of the breakers marked converter?
If so, find EVERY outlet on that circuit breaker, that converter will be plugged into one of the outlets on that circuit..
Do you have any storage compartments up front near the battery?
If so, converter might be there..
Have a front passthrough storage compartment?
Converter might be in there..
Have dinette seats?
Look UNDER the dinette seats, converter may be there..
Look under your kitchen cabinets, might be under there..
On the outside, check the tongue for extra connections from the battery, there often is a little silver box with two terminal studs, that is a circuit breaker for safety.
Looks like this..

Circuit breaker often is used for a place to add extra wires like converter or tongue jack and they only run one wire to the battery. Then trace the wires from the breaker..
You are going to have to look at every nook and cranny in all of the lower base cabinets, under beds, under the stove, under the fridge, every single outside accessible storage area.