Transferring images from SD card to internal storage

[AC Question]

I wish to to transfer images from my camera SD card to my Tab S. I have bought an OTG cable and connect this to the card reader and then connect to the Tab S. In My Files I can access the folder and images but cannot find any way of transferring them to the internal storage. There is no copy facility and dragging and dropping puts the folder in My Favourites but as soon as I disconnect the OTG cable the folder disappears. I've spent several hours reading online comments but nothing solves the problem, please help. Thanks