trying to find preferences.plist file
The location of the file has not moved. It is still located at /Library/Preferences/SystemConfiguration/preferences.plist.

Please make sure you are not in your User's Library folder (~/Library/Preferences/).

The best way to go to the correct folder in Finder is to use the menu item Go &gt; Go to Folder..., or press cmd+shift+G, and enter the folder you need to go to. In this case, /Library/Preferences/SystemConfiguration/.