All of these losers are giving you bad info OP. You should listen to a loser like me. Try booting into recover mode and running checkdsk /f /r. It should at least repair the partition enough to view. Copy your things off and start a fresh SD card in your 3DS. Shut it off and copy & replace the files. Start it back up and it should be functional enough for you to get your saves off of it. If your disk is in use when in recovery open diskpart and offline it prior to running chkdsk.