Welcome to the forum. You're making a wise decision to replace the tires.
A RV dealer would not be my first choice to buy tires, unless you know and trust the dealership.
Find a tire store you trust.
Replace your tires with the same size and load rating. A good tire store will tell you if you need a different tire.
The make of tire is your decision. Some on the forum will tell you Michelin is a good choice.
I like Hankook, I've used them for years with good results.
Check and see what tires are available in your area, then post it on the forum, You'll get several opinions on each make.
Don't buy tires based on price alone.
And, check the date code on the tires when you purchase them, you don't want to buy old tires.
Enjoy your travels.