Where does an SD card go in an amazon fire tablet?

This is completely silly but hoping mamas can help! We recently started traveling and used my daughter tablet for a plane ride but due to her memory space , it was pretty useless in what we wanted to use it for. It’s an Amazon kids fire tablet, the latest version I think, that’s purple with a design on the back. I read somewhere that you can buy an SD card but when I was looking at the tablet-under the case , I can’t for the life of me see where an SD card would even go? I can’t imagine I’m the only mom with a kiddo with a tablet or even has had this struggle , so trying to figure out where to put it before I buy one !