Total Commander is about the easiest way. Hold the phone in landscape mode and you can have both folders open at once - where the files are and where you want to put them. Drag and drop. Tap Copy. If the copy is successful. long-press the file on the SD card and delete it. (If you Move and something goes wtong, you can lose both the original and the copy. If something goes wrong in copying, you still have the original. The same as with Windows from one drive to another.)