Well if you are only wanting to transfer photos, music, videos, etc., to the SD card, you just need to connect that tablet to a computer via USB cord. Then move the files into a folder on the computer and then copy them back through the same USB connection to the SD card.
Now, however, if you are wanting to move apps, that is a whole other thing. For that you would need to have a tablet that is 1. running at least Android "Marshmallow" and 2. has not had this option restricted by the manufacturer (which does happen). I am including the instructions on how to make the change below. If any of the steps don't work for you, or an option is missing on your device, then it has been restricted by the manufacturer.
How to turn the...