Package files from the extracted folder into your Mods folder. Now just double click on the 7z or RAR file (like you would a normal Zip file) and The Unarchiver will extract the contents into a new folder in your Downloads folder.The downloaded file will now look like one of these in your Downloads folder: Download The Unarchiver from the App Store.
I don’t normally like any software that overrides Apple’s Apps but I’ve been using this ever since my CC obsession started and had no problem with it. It’s really simple to use as it sets itself up as the default unarchiver on your Mac so once installed you don’t have to do anything. The best tool I have found to extract 7z and rar files is The Unarchiver and you can download it straight from the Mac App Store here. I was late to the CC party and experienced this as the built in Archive Utility in macOS can’t handle 7z files. Lots of Simmers, Mac and Windows users, still have issues installing CC and Mods into their game because of the compression methods some creators use.