How to upgrade a MacBook Pro (13-inch, Mid 2012) from macOS Sierra 10.12.6 to a new MacOS ?

The model year of a MacBook Pro is available at Apple menu > About This Mac.

A mid-2010 through late-2011 MacBook Pro can be upgraded to High Sierra 10.13.6 but no later version.

A mid-2012 through early-2013 MacBook Pro can be upgraded to Catalina 10.15.7. See: https://support.apple.com/en-us/HT211683

A late-2013 or later can be upgraded to the current version of Big Sur. See: https://support.apple.com/en-us/HT201475

The Age of this computer will Govern what newer version of macOS it will Qualify to install. Use About this Mac from the Apple Icon on Desktop - the required Information will be there.

With the above information in-hand - follow this How to get old versions of macOS and verify what version this computer Qualifies to install. Make sure to use Only Safari to commence the download as Other may not work

Make a Time Machine Backup Before attempting. Notation - Mojave is the Last version to support 32 bit applications / extensions and Drivers. Catalina and Big Sur Only support 64 bit and there is not workaround.

Are there any AntiVirus, Disk Cleaner, Optimizers, Defrag, VPNs etc installed which should be removed as per Developers Instructions. They are useless, unneeded, cause havoc and interfere with the normal operation of the OS and may even Corrupt the OS requiring a Reinstallation.