Here's what my electric system looks like. I'm pretty sure the breaker box and big cord are original.
I only have one outlet and it is on the left side of the trailer along a seat edge. There may have been a 2nd outlet somewhere but would have disappeared with a previous owner.
It is too far away for most short-corded kitchen appliances and is only a single outlet.
So I added a multistrip outlet nearer the kitchen area. Looked hard to find one with a plug that hugged the outlet rather than stuck out.
The big cord is supposed to snake through a hole in the floor. My hole is at the center of the left photo and is stuffed with steel wool to keep critters out. Brass wool is better but I haven't noticed any rust on the wool.
But snaking the cord in and out of the hole is a pain in the bottom. So I just keep it coiled up and run the proper all weather extension cord from the campground box up into the hole.
That sends power to my outlet and to a lamp on the wall. Care should be taken not to overload that one outlet. I have no trouble running a small heater, the light
, and a fridge
but if I had a microwave
or a toaster oven I'd probably turn off the heater while using them.
How about some photos of your Jr?