Is it a laptop or a desktop?

Desktop self-built: suitable screws - often referred to as "SATA screws" - are often included with the enclosure.
Desktop ready-made: when replacing HDD/SSD you can often use the same screws.
Laptop: see "Desktop ready-made

If you need new screws, they are called "M3 screws" (regarding diameter) and the length should be as short as possible. The best way to look for the right screws is to 1) know that you actually need them and 2) know how long they should be.

And: you are not the first to wonder about SSD screws :) https://www.google.com/search