2000 grand am radiator filler cap

I have a 2000 Grand Am. I need to add coolant but when I remove the cap on the bottle, there is a plastic part underneath that didn’t come off. Should this screw off, or do I simply pry it out.

I’ve got a 1999 Grand Am and on mine the cap pops off. There is a a block ring attached, that keep me from misplacing it. It stays attached to the neck of the tank. If yours is just the ring, the piece the attaches it to the cap probably broke off.