I need to upgrade to Mac OS 10.12 or later

It all depends on what Mac model and year your Mac is, check the compatibility of your Mac against these guides,

How to upgrade to macOS Mojave - Apple Support

How to upgrade to macOS High Sierra - Apple Support

How to upgrade to macOS Sierra - Apple Support

Check to make sure your applications are compatible.        

Application Compatibility

macOS Sierra 10.12: Compatible Apps

Also check to make sure there is a compatible driver for your printer.

Do a backup before installing, preferable 2 backups on 2 different drives.

If your Mac is capable of Sierra, then it is capable of High Sierra.