There's only one campground in Yellowstone that has hookups:
Fishing Bridge CampgroundYou'll have folks saying it's a 'parking lot' but you be the judge from these tree-filled pictures. :) It's very convenient for doing your full days of driving around the park. The park is huge.
There are many other campgrounds in the park but they don't have electric although there are generator hours and dump station in some.
Yellowstone Campground MapAll Campgrounds in YellowstoneConsider including a visit to Grand Teton National Park which is right next door. A 3-night stay there would be a good introduction. It is completely different from Yellowstone. The hiking trails are gorgeous for many abilities. Take the gentle Snake River float trip through the park and you just might see a moose or two in the water with you! Colter Bay RV has the hookups in the park. Right next door is Colter Bay campground (300 sites), no hookups. Gros Ventre closer to Jackson also has 300 sites.
Jackson will be your spot for replenishing your food supplies. There are two major groceries just south of town - Albertson's and Smiths. When you get to Yellowstone you'll only find some country stores with staples and higher prices. Have a great trip!
