Question: how to transfer files from internal storage to sd card in samsung j2 prime?
Answer: Go to device “Settings”, then select “Storage”.
Select your "SD Card", then tap the “three-dot menu“ (top-right), now select “Settings” from in there.
Now select “Format as internal”, and then “Erase & Format”.
Your SD Card will now be formatted as internal storage.
Reboot your phone.