If your MacBook Pro is a 2015 or later, you should be able to use the following instructions: How to upgrade to macOS Monterey - Apple Support
If that doesn't work, you may want to reply with more details about what happens when using those instructions.
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. See: How to get old versions of macOS - Apple Support
A mid 2012 through early 2013 MacBook Pro can be upgraded to Catalina 10.15.7 but no later. See: How to get old versions of macOS - Apple Support
A late 2013 and mid 2014 can be upgraded to the latest version of Big Sur macOS 11 but no later. See: How to get old versions of macOS - Apple Support
An early 2015 or later can be upgraded to the current version of Monterey macOS 12. See: How to upgrade to macOS Monterey - Apple Support