How do I move my mods folder from disk C to D?

You can't do that with only the mods folder. Are you on PC or Mac? I'll move you to the right tech support area.

In the meantime, the easiest thing to start with is to delete the content you aren't actually using. 

I’m on PC. If I can’t move only the mods folder then that’s fine, I can move the entire documents folder as long as the game reads it, if that actually works.

i do this because my G drive is the only NVME disk gen 4 that i have, i create a SymLink

To create a symbolic link from G:\SimsMods to D:\Users\[ThisISMe]\Documents\Electronic Arts\The Sims 4\Mods, you can use the Command Prompt in Windows. Here’s how to do it:

Open Command Prompt as Administrator:
Press Windows + X and select Command Prompt (Admin) or Windows PowerShell (Admin).
Use the mklink command:
Type the following command and press Enter:

bash

mklink /D "D:\Users\[ThisISMe]\Documents\Electronic Arts\The Sims 4\Mods" "G:\SimsMods"
Here, /D specifies that you are creating a directory symbolic link.
Verify the symlink:
Navigate to D:\Users\[ThisISMe]\Documents\Electronic Arts\The Sims 4\Mods in File Explorer to ensure that the symlink has been created successfully.

This will create a symbolic link in the Mods directory that points to the SimsMods directory on your G: drive.

BoujeeCiasto​  Do you still need help with this?  The command you've listed assumes your Documents folder is on D, not on C.  I would also strongly suggest labeling the folder on G as Mods, not SimsMods, as the different name may cause problems for the game.  Or it might not; I haven't tested this.

yeah sorry i didn't adapted it fully i just censored my name i have multiple hard disk to different task and D is just for documents as you need to use it you need to take this steps 

*make sure you move your mods or pref your entire "the sims 4" folder to your desired location, the other disk

*make sure the documents folder is empty and the target "D:\Users\[ThisISMe]\Documents\Electronic Arts\The Sims 4" if you include the saves Etc... [ThisISMe] should change your user profile, i censored it because in windows is the same as my personal mail

*copy the command 
mklink /D "D:\Users\[ThisISMe]\Documents\Electronic Arts\The Sims 4\Mods" "G:\SimsMods" 
in notepad and edit the nesesary parts to match with your needs

*open CMD, just search cmd and right click open as administrator, left click open will generate error, copy the notepad text and in the cmd window right click, this will paste the text (Ctrl+V works too)

puzzlezaddict​ you can test it and ensure it works, to me a heavy 10k+ CC plus graphics enhanced packs load 5 minutes faster than my slow ssd