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if you're just talking about the dcim folder leave it there. Your camera will need it to save images the next time you use it. If there are still files in the dcim folder then using my files tap on the dcim folder, tap on the camera folder, tap on menu and choose select all. Now tap on the trashcan icon. That should do it.

Do you mean that the photos are still inside the DCIM folder?

I think your memory card is corrupted or something. Try backing up the contents to a PC then reformatting it.
You mean you can't open the card on a PC, to get to any file? Do you have a MicroSD to SD adapter?
EDIT: forgot to ask, does your microsd have a little white switch at the side, with an arrow that says "lock"?
On some microsd cards, there's a lock switch that activates write protection.