As a quick fix so you can use your camper before doing electrical
work extension cord and power strip will work. On the power strip get one that has a). a circut breaker. b). has what look like regular wall plugs coming through the housing.
b) is because the flat plastic power strips with the plug slots molded in are incredibly low quality inside. The ones that are a box with real outlets in them are much better, and safer.
As noted by others you will have more plugs than your extension cord/circut breaker can handle, fridge
draws extra power to start, anything that produces heat like a heater, coffee pot, toaster, blow dryer etc. will draw a lot. Charging you cell phone or laptop not so much.
So brewing coffee, with the heater going and having the fridge
start I'm pretty sure will trip your breaker.
Long term you really want a small box that has a circut breaker or two, with a really heavy "pig tail" extension cord of moderate length wired to the circut breakers. You pass the pig tail out of the trailer (through a cord port I'm sure you have) to plug in, only use an extension cord outside on that pigtail if your not close to electric hookup.
Wiring in a breaker box and a couple of outlets and lights
is not a complicated job, I bet you know someone who has added an outlet or light
to their home, not any different in the camper. Invite them over to help, make em something good on the BBQ grill.
Do one outlet and light
with help I'm sure you you can do the rest. But it's always easier to get started with a little help and advice on the scene. Do a little google time on wiring a plug, and you will see it's not as difficult as a lot of things you are already experienced at. Just new.