Need Overnight stop I77 Southbound south of Charlotte

I think the OP is just looking for a place to sleep for 6 hours, not really a campground. We have stayed at Cracker Barrel restaurants before. There is one close to the NC/SC state line. There is also a Walmart in Rock Hill, SC (just south of Charlotte). You could probably find a spot there that you could extend your slideout. If you want a campground there are several very close to the NC/SC state line including a KOA, Carowinds campground and as someone else mentioned Ebeneezer Park outside of Rock Hill.