How do I change SD card back to external storage?

[augerin]

When I was running on Android 5 my SD card was external storage. I updated to Android 6, did a factory reset and restored with backup from Smart Switch. Now my SD card is internal storage. I cant save anything to SD card because phone doesn't recognize it as a SD card. When I restored phone from Smart Switch I didn't have SD card in phone, but put it in later. Does that make a difference and is there a way to fix this?
Thanks