Do you guys know how to transfer my mods folder to my D drive?

1. You can move your entire user folder to another drive which will move all the settings of your Sims 4 game with it. You need to use the windows procedure to move it so that Windows knows this is were your Document folder is. 
2. You can move your mod folder itself to a different drive and then in make a persistent symbolic link to the new folder to \Documents\Electronic Arts\The Sims 4\Mods . This is a command line procedure and can be complicated if you don't have much computer experience. 

Make a backup of your data before you do any of this work. 

[CM Edit: Links removed]