Upgraded to Marshmallow, now all mp3's can't be found

After the upgrade none of my mp3’s can be seen on my Sandisk card that’s in my Samsung phone. The card held 13 gb of mp3 files before and now it still says 13 gb so I think they are there but I cannot access it, it doesn’t show any of them (and there are a few hundred). What can I do to retrieve these mp3’s. Any help is most appreciated.

If you was using card, then may be your card is crashed or formate due to software update. If you have backup then restore the files or if you don’t, then you can use any data recovery app and can restore some of your data.

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