Can I scan using Canon Printer MG 7120 with Mac OS Monterey?

Yes, and you can do it using AirPrint also. The MG 7120 is one of many on Apple's list of AirPrint capable printer/scanners.

You can do this through System Preferences > Printers and Scanners > Scan > Open Scanner

This produces some controls for scanning. Make your choices and scan.

And another tip - If you save the printer control panel to your Dock it is easily found for next time.

Also refer to your printer manual.

I am unable to scan from either the menu window on the printer or when I open up the system preferences and select printers/scanners the scanner option doesn't appear, just print.

Try resetting the Print Center:

If you hold down the Control key as you click in the Printer list a pop-up message appears giving you the option to Reset printing system.

This will erase your printer list and you can add your printer as if it were a new one. Perhaps this might clear the problem you are having.

If that fails to resolve your problem you could reinstall the scanner driver which you can get from here. This would be the one labelled ICA Driver Ver.4.1.3a (Mac) and is dated 2021. I presume it is September in the odd way Americans write numerical dates : )

By the way - I congratulate you on having a printer last nearly a decade - this one is from about 2013.