I got an old Dell Optiplex 7040 Tower cheap. Using as a home media server. It came with a 2.5" SSD which I am using as boot drive. I want to add an existing 3.5" HDD which has a bunch of movies and music on it. (Specifying existing, because obviously if I were getting something new it would be SSD.)
The hard drive caddy is weird, and I can't figure out how to fit the HDD in it. With existing mounting screws, it won't snap in. If I remove the screws and put the HDD in the caddy, the screws are too short to secure the HDD. (For ease of reading, all images are at the bottom.)
If I put in two screws, I can slot it in, where it sits loosely. I can't fit it in with four screws.
The caddy slides into the bay and snaps into place, which is convenient, so I think the solution is just to get the right kind of screws. However, I'm also seeing versions of the caddy online that look like they have threadless mounting pins: https://www.amazon.com/DBTLAP-Compatible-0CW33-OptiPlex-Bracket/dp/B07WSDKWG7. I can't even confirm from the Dell manual that this is the correct part number (0CW33), and don't want to order a caddy that doesn't actually fit.
Asking for advice on correct screws, mounting pins, or caddy.
This is the caddy:



Hard drive with two screws:

Typical hard drive screw:

The hard drive caddy is weird, and I can't figure out how to fit the HDD in it. With existing mounting screws, it won't snap in. If I remove the screws and put the HDD in the caddy, the screws are too short to secure the HDD. (For ease of reading, all images are at the bottom.)
If I put in two screws, I can slot it in, where it sits loosely. I can't fit it in with four screws.
The caddy slides into the bay and snaps into place, which is convenient, so I think the solution is just to get the right kind of screws. However, I'm also seeing versions of the caddy online that look like they have threadless mounting pins: https://www.amazon.com/DBTLAP-Compatible-0CW33-OptiPlex-Bracket/dp/B07WSDKWG7. I can't even confirm from the Dell manual that this is the correct part number (0CW33), and don't want to order a caddy that doesn't actually fit.
Asking for advice on correct screws, mounting pins, or caddy.
This is the caddy:



Hard drive with two screws:

Typical hard drive screw:
