That may not be the card but just a cover over the slot where the card
reader would be. The card is intended to be easily removable and
replaceable in flight. Unless the card comes out easily and your unit says
800 Plus on the back, there is no card reader installed.

I just checked with Garmin (now the owner) and the cardless 800's are not
upgradable because the required memory chips are no longer made.

--
Roger Long