Well, it is going to depend on what version of Android your device is running. If it is running anything prior to "Marshmallow" then it won't work. However if you have "Marshmallow", or can upgrade to it, then it should work. Unless of course the manufacturer has restricted that option on your phone, which does happen.
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...