With 6 bolts, just get your ruler and measure. Probably 6 on either 5 1/2 inch, or 6 on 6 inch. Should be able to measure straight across the hub. Just use your eyeball, it will be one of the two.
Other option, go under the camper and try and find the tag on the axle, then go to axle website and see if you can find it there.
Don't forget you will need to know the width of the wheel also, I would guess between 6 and 7 inches, again in 1/2 inch increments.
2012 Ford F250 ext. Cab 4x4
2002 Jeep Wrangler Sahara
2008 Yamaha V-Star 650 Classic
2008 Work and Play 18LT