SD not detected afte rupgrade I just updated to Android 6. I am getting a notification that a new SD card is detected. If I format it it will erase everything. It has loads of stuff I want on it. What do I do?
You can compare your situation with the screenshots in our adoptable-storage tag-wiki: what's going on here is Marshmallow asking you how to deal with the card (it asks only once). If you chose to use it as "internal storage", indeed all its contents will be deleted (see tag-wiki again for details). But if you chose to keep it as "portable storage" (i.e. the same way it was used before), your data on it will remain intact – as Death Mask Salesman just confirmed in a comment on the question itself.