Welcome, Helen!
If it has a "Coach Body" it's a Class C. Some call them "B+" but technically a B is build inside or mostly inside a panel van's body. A C, whether it has cabover bunk or just a fairing with entertainment center, is built on a CutAway van chassis. The factory sheet metal stops at the door frames, doesn't even have a back wall. Coach body takes over from there.
There may be a sticker in the door frame from the coach builder saying what the "new" wheelbase is if the chassis was stretched. Ours has two stickers. One from Ford saying 158" and one from Jayco saying 218" for a 60"/5-ft stretch. It's also stretched behind the axle.
I'd guess yours is an original 158" but it's easy to measure. Drop lines from the centers of the front and rear hubs to the ground, measure between them.
If God's Your Co-Pilot Move Over, jd
2003 Jayco Escapade 31A on 2002 Ford E450 V10 4R100 218" WB