how do i upgrade my operating system to system higher than I'm running macOS sierra 10.12.6
How do i upgrade my operating system to mac0S high sierra
iMac 21.5″, macOS 10.12
You’ll be able to upgrade at least as far as High Sierra, maybe further:
How to upgrade to macOS High Sierra - Apple Support
Maybe to Mojave, the last release that supports both 32-bit and 64-bit apps:
How to upgrade to macOS Mojave - Apple Support
Or to Catalina, the current and 64-bit-only release:
How to upgrade to macOS Catalina - Apple Support
If you upgrade to Catalina, you’ll need to find (Go64) and upgrade or replace or retire any 32-bit apps.
Whichever you pick, it’s a direct upgrade. And have complete and current backups.