it's telling you to format the card as there's an error on the card, some further info below about memory cards and how to look after them with the camera which may be useful also
formatting in the camera just resets the allocation table but that may not clear an error on the card, if you see it repeatedly you may need to reset the card back to its default state first, to do that use SDFormatter
https://www.sdcard.org/downloads/formatter_4/ (whichever version is appropriate for whatever PC you have) and do a full format (don't do the quick format), this will return the card back to the default settings as per when it was new, after that completes successfully the card will need to be formatted in the camera prior to use
things to do to keep things healthy,
if you access the card in another device, PC, phone, tablet etc make sure to eject the card safely, don't just unplug it
copy files off if you want but don't delete or edit files on the card from another device
format the card when you put it back in the camera
make sure to use the supplied (or one of the approved replacement) power supplies
deleting files from a Mac is the number one culprit for causing this issue, if you don't empty the trash on the Mac before ejecting the card you can pretty much guarantee it is going to have an issue with the card, when you get a chance I would definitely recommend going through the full format process with SDFormatter to get things back to how they should be