upgrade to macOS monterey
upgrade to monterey from sierra
iMac 27″, macOS 10.12
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. For Best results use Safari to commence the download as Others may not work.
Safari will open a redirect and open the Apple Store where the download can commence.
If this is Production or Mission Critical setup, would seriously suggest doing a gradual upgrade from OS X Sierra to at least Catalina macOS 10.15 First.
There are a lot of changes that have occurred since 2016 in the way macOS functions.
Computer Hardware also comes in to play.
Does the computer have a Traditional Rotational Drive which will suffer slowness starting in Catalina .
Does the computer have at least 8 GB of RAM ?
It will work with least but will really limit the number of Applications that be open at the same time
Computer Qualify for the Monterey upgrade
macOS Big Sur 11 hardware requirements
macOS Catalina 10.15 hardware requirements
macOS Mojave 10.14 hardware requirements
macOS High Sierra 10.13 hardware requirements
Make Time Machine Backup is very useful
Notation - Mojave is the Last version to support 32 bit applications / extensions and Drivers. Catalina, Big Sur, Monterey, Ventura supports only 64 bit and there is no workaround.
Suggest using Go64 to find 32 bit application before attempting the upGrade. Some or many of the Application already installed may require an update or upGrades to 64 Bit Version
