>M3x3mm
You are looking for something like this.
You’ll just need screws then. I found this on Amazon. An SSD is able to transfer information faster than an HDD, so it is typically used for booting up the laptop. The HDD is usually for massive file storage.
Literally the first link that popped up when I googled it.
The screws should come with your SSD, if not you can buy them for cheap on Amazon.
Something like this is what you need
https://www.amazon.co.uk/Laptop-Drive-Screws-M3x3MM-PM3X3-0/dp/B00B1UVKSY
Something like that?
Not sure what country you're from but UK amazon have them.