Summary: You don't need to add a lot, you might want to add a little and you can get rid of some things that you don't need any more.
We had a tent, followed by two Pop-Ups then went o hiatus for a while and got a travel trailer last year. So many more systems to worry about, but much more convenient.
We saved and moved over much of the stuff over (kitchen utensils, bbq stuff, etc.)
We needed a sewer hose since the pop ups did not have toilets and gray water just went into a jug and drained. Also added toilet paper.
With more room, we added some convenience items such as a coffee maker, electric skillet, and crock pot.
New unit has a 30A cord, so we got a 20A to 30A adapter (so we can plug in at home, too.) Have a 10 gauge extension cord that we moved over. That works unless we need A/C, so I've got a 30A extension cord on my Xmas wish list.
I made a towel rack to help get towels dry. In the popup, we could run a line under the slide out ends and dry towels there.
We have plenty of storage room and have not managed to use it all up yet. We got some plastic bins to hold items in the pantry.