Can I install Mac OS Monterey on the following: IMac (Retina 5K, 27-inch, Late 2014?

No. For that Mac, Big Sur is the end of the line.

If your iMac is not running Big Sur yet, you can get it from here:

How to download and install macOS - Apple Support

Note that Catalina and Big Sur will not run 32-bit applications. If you're on Mojave or earlier, you may want to check which of your applications are 32-bit (and will need updating/replacing) before upgrading.

Just to add

If upgrading to macOS 11 Big Sur

Suggest having at least 50 GB of Empty Space on the drive.

It will allow the Full Version ( about 12.xx GB ) to download, then expand and then commence to install.

If there is Third Party Security Software installed - remove it.

It will interfere with both the download and installation process.

Always Make a Time Machine Backup  before doing any upDates / upGrades