sharing power for a fv

ok i hope this is the right place to ask this type of question .We have a Chevy van set up for camping we have one battery for starting to van and two house batteries that charge off the alternator when we drive and power camping items such as coolers fans lights etc with out draining the start battery of the van all works great we can also use shore power when we can plug in and we have a trickle charger to keep house batteries charged up ad we camp.Question is we now have a small camper with a 7 pin connector which among other things charges the camper battery .We want to know is there some way to have an outlet on the outside of our van such kinda like our shore power outlet that we can run to the camper and use the power from van house batteries to make camper run on battery longer when dry camping if so what guage wire do we use to what kind of outlet and what kind of extension cord?

Do you mean like a wall outlet receptacle? Which is 120 volts. The plug in is 120 volts AC. No. You cannot step up a 12 volts to a 120 AC volts alternating current, like a wall outlet. Which you want to connect TV, radios, electric stoves. Yes. Solenoid, goes up to 22,000 volts. All you need is 120 volts. How to? There is a lot to this problem.