Solved! galaxy s4 portable storage

Solution
You would have to move all files that are on the card to either the phone itself, a cloud account or a computer. Then any apps you have on the card will either have to be moved back to the device, if they were originally on the device that is, or they will have to be uninstalled and then reinstalled on the phone itself, if they were installed directly to the card.

Once everything is off the card, or everything that you want to keep that is, then go back into the phone's settings and change the card back to "External" storage. It should wipe the card.

NOTE: It is impossible to make the card "External" storage again while keeping anything currently on it while converting it. Anything on it will be wiped.
You would have to move all files that are on the card to either the phone itself, a cloud account or a computer. Then any apps you have on the card will either have to be moved back to the device, if they were originally on the device that is, or they will have to be uninstalled and then reinstalled on the phone itself, if they were installed directly to the card.

Once everything is off the card, or everything that you want to keep that is, then go back into the phone's settings and change the card back to "External" storage. It should wipe the card.

NOTE: It is impossible to make the card "External" storage again while keeping anything currently on it while converting it. Anything on it will be wiped.
 
Solution