The Age of this computer will Govern what newer version of macOS it will Qualify to install.
Find out which macOS your Mac is using - Apple Support (CA)
Does this computer appear as Listed and qualifying for an upGrade to a newer version of macOS ?
With the above information in-hand - follow this How to get old versions of macOS and verify what version this computer Qualifies to install.
Safari will open a redirect and open the Apple Store where the download can commence.
If Yes, 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.
The below links will help identify which version of macOS this computer may Qualifies to run.
macOS Monterey is compatible with these computers
Always make a Time Machine Backup before doing any upDates / upGrades