I understand you would like to know how to restore data from internal storage to external SD card.
Don't worry I'll try to help you out.
Did you make any changes to your tablet?
Try few steps recommended below.
The workaround would be to get a file manager through google play. If you do a search for file manager you will get tons of results. Some of them work better than others, so be sure to check out the reviews. You will likely want to look for one that has a "move to" function built in. A lot of these managers will make you copy the file, then browse to where you want, then paste it. The move to function will give you a menu right away to go through the folders and select the location so it will be a smoother process.
Refer this article to know more information about Transferring and Backing Up Files.
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