Note: You asked about a tablet but posted in phones. That said...
You would need to be running at least Android "Marshmallow" to run apps from the card. Which is Android 6.0. If you can upgrade to that, then you can run apps from the SD card. Otherwise you won't be able to. If you can upgrade to "Marshmallow" then these instructions will help you.
How to turn external SD card into internal storage on "Marshmallow".
NOTE: Please be sure you start with a blank SD card. It needs to be blank because when the card is converted to "Internal" storage, it will be formatted (wiped) and encoded (making the cards data only readable by that device).
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 tablet.
NOTE: If you don't reboot the tablet, many things may not work correctly, so make sure you do.