How to update my Mac from Sierra MacOS?

Back up your data, check the application compatibility table, click here, and then on the download link for a more-recent OS. A Mac running Sierra can be upgraded at least as far as High Sierra.

Catalina and higher won't run 32-bit software; if you upgrade to one of them, use Go64 as well.

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The simplest way is to open System Preferences and select Software Update. It may be under General. If it says no updates available then you are likely already on the latest version of macOS your Mac can run. Have you tried this and what was your result? But as master volunteer Noel points out, sometimes updating macOS gets you into trouble with existing apps that are not compatible with later versions of macOS and may require updates, not all of which are free.

What version of macOS you can run is entirely dependent on what year/model of Mac you have.

There isn't a Software Update pane of System Preferences in Mavericks through High Sierra.

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