Try to upgrade my MAC OS from high sierra 10.13.6 to catalina 10.15
Not found in App store or system reference.
Is this upgrade supported
Back up your data, check the application compatibility table, click here, and if your Mac is a 2012 or newer model(2013 for desktop Mac Pros), then on the download link for it.
Catalina and above won't run 32-bit software; use Go64 as well.
(242843)
Which upgrades—Apple calls bigger and potentially app-breaking changes upgrades, and smaller changes are called updates—are available depends on the Mac model and Mac model year.
Here is: How to download and install macOS - Apple Support
If you want us to check which upgrades are available, post the Mac model and Mac model year from the Apple > About This Mac… menu item.
Model is Macbook pro
Model Year 2013
If it's a late 2013 model, it can run Big Sur; otherwise, proceed as described above.
(242845)
Why I cannot find update in app store for my macos high Sierra to catalina
