If you have changed the phone by rooting it, then you should post the query in the "Rooting, Jailbreaking & Unlocking" Forum.
http/www.tomsguide.com/forum/forum-117.html They could better help.
If you have not rooted it, however, then if it will work or not is going to to depend on if the phone is running "Marshmallow" or not, and if the manufacturer has restricted that option on that device.
To start (if you are running "Marshmallow") you will need a blank SD card. Why? Because when the card is formatted and encoded to be "Internal" storage rather than the typical "External" storage, the process will wipe any data that is already on the card. Also, the card will then only be readable by that particular device.
How to turn external SD card into internal storage on "Marshmallow".
1. Go to device “Settings”, then select “Storage”.
2. Select your "SD Card", then tap the “three-dot menu“ (top-right), now select “Settings” from in there.
3. Now select “Format as internal”, and then “Erase & Format”.
4. Your SD Card will now be formatted as internal storage.
5. Reboot your phone.
NOTE: If you don't reboot the phone, many things may not work correctly, so make sure you do.