Well the tablet should be running windows "Marshmallow" and if it is, then turning the SD card into "Internal", rather than "External" storage should be possible. Unless the manufacturer has restricted that option. Which does happen.
Before starting, you will need a blank SD card. Why blank? Well when you change the card to "Internal" it is formatted and encoded to that device. So anything on it will be wiped, and the cards data will then only be readable by that 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...