PP will rebuild those files when you reopen the project that needs them. Best to have those on their own drive...
...or at least off the C: drive...
Macintosh uses names for volumes, not letters.
If you go to the Edit Menu, and select Preferences, and the Media tab, you will find two "Browse" buttons. You should use these to shift your Media cache off your C:\ drive onto another fast drive in your system - ideally not the drive which contains your media files. Create an Adobe file on the target drive before you start, and navigate to it when you browse.
You can then safely delete your exiting cache on your system drive, and Premiere will re-create the files it needs in your new location. It is a good idea to use the "Clean" button on the Media tab at intervals to remove all the files which are no longer required.