I bought a used Charles Daly Field Hunter VR-MC 12 gauge On the barrel it states 3 inch does this mean you can only shoot shells or 2 and three quarters as well?

Yes, you can shoot both 2 3/4-inch and 3-inch shells in your Charles Daly Field Hunter VR-MC 12 gauge shotgun. The "3 inch" marking on the barrel indicates that the shotgun is chambered for 3-inch shells, which are the longest shells that can be safely fired in this gun. However, the shotgun can also safely fire 2 3/4-inch shells, which are shorter than 3-inch shells.