Based on my research your 2011 Forest Rive Flagstaff Mac pop-up camper does have a 3,000 lb GVWR like you mentioned. For safety chains a great option will be the Curt Single Hook, Coiled Safety Cables with S-Hooks - 42" Long - 3,500 lbs # C80136.
I've added a link to a video review of these chains for you to check out as well. view full answer...