Please try the following.
1. From a Home screen, go to... "Apps", then "Tools", then "File Manager".
2. Tap "All files".
3. Tap "Internal storage".
4. Tap the applicable folder (e.g., Music, Pictures, etc.).
5. Select a file or files.
6. Tap the "Move" or "Copy" file manager icon (located at the bottom).
7. Tap (check) the desired file or files.
8. Tap "Copy" (located in the lower-right).
9. Tap "SD card".
10. Navigate to the preferred destination folder then tap "OK".
Note: Steps 9 and 10 can sometimes need to be done in reverse, depending on your OS.