These files go in the Tray folder in the Sims 4 documents (Documents/Electronic Arts/The Sims 4/Tray).
You can create additional subfolders to organize your growing mod collection better. Open the Mod folder the game has created (Documents/Electronic Arts/The Sims 4/Mods) and copy all the mod files into the folder. The folder is usually found in this directory: Once you’ve enabled mods in Sims 4, the game will automatically make a Mods folder in your Sims 4 Documents folder. After the game receives a new patch or update, these settings may disable, so you’ll need to go back and re-enable them.
Installing mods may sound simple, but it’s composed of a few steps and can take a while, depending on the file sizes you’re downloading. The process is slightly more challenging for mods than custom content (CC), but both follow a similar installation pattern. The great news is that mods aren’t complicated to install, but you still need to pay attention to some detail to get the most out of them.