Update from macOS High Sierra 10.13.6 to 10.14
I have MacBook Air 2017 and its running on macOS High Sierra. I have also MS Office older version which is to be operative till December 2020.
AppStore shows my system is updated. When I try to install MS Excel Productivity it fails as it requires 10.14. Pope up says can’t be installed on “Macintosh HD” because macOS version 10.14 or later is required."
Please help how to update my macOS when its not available in AppStore
MacBook Air 13″, macOS 10.13