Probably the same things you took with you in the P'Up.
If you can, it's usually recommended that you "driveway camp" before you head out om a trip with a new RV. You guys are seasoned campers, but as you know, there will be things that you forget. Spending a night, and doing the things you would do on the trip (while at home) will save you any aggravation later on.....or at least reduce it:B
On our first trip, we forgot to take our clothes...LOL!! Left the bags sitting on our bed at home. Fortunately, it was only a weekend, so we got by, when we stopped off at Walmart for some underwear, toiletries, etc:B
One thing you might want to get is adapters for the shore cable. I don't know what the connection was on the P'Up, but you might want to get a 50A to 30A and 30A to 20A adapters, in case you need them at the CG you go to.
Sewage hose would be good too, if you didn't have one in the P'Up, as well as the fittings and such. I'll assume that you bring over the white water hose from the other camper.
So, my advice (which I didn't take) is to camp at home one or two nights.