question: How to find out which version of macOS you’re using
answer: 
  What can a VPN do?
  Show Me
  
  This guide will show you how to find the version of macOS (previously Mac OS X) on your MacBook, MacBook Air, MacBook Pro, iMac, Mac Pro, or Mac mini.
  
  To find the version of macOS on your device:
  
  Click  > About This Mac.
  The version name and number will appear at the top.
  
  See the supported version of ExpressVPN on different Mac operating systems.