Welcome to the forum
These screw-less cases can be a real pain to open. They do open though, otherwise they wouldn't be able to get a drive inside.
If you look at the back of the case, or the bottom, and see if you can separate two parts of the case at all. If a gap does open up, you'll have to use force to open the case the rest of the way. Be careful not to break the fasteners, or you wont be able to get the case together again.