Have you downloaded the client from the FAF homepage (https://www.faforever.com/), started it and logged in? If yes, look at the top for the "Vault" tab and then select "Mods" at the left.
The mods are made to work with the current FAF game patch. Even if you could download them manually, you still would need your game to be patched by the client to the current FAF patch. So you need the client unless you want to do all of that manually, which you don't.
Hey, you can get Mods from Moddb, just google Supreme commander mods and Moddb will show up!
But why not try out the Client where you can easily manage mods and maps from the vault and it has the most mods and the most recent updates and most new mods are on there, like my mod, so why not try it!
I have created a mod, yes and it's awesome. CHECK it out!