The Age of this computer will Govern what newer version of macOS can be installed. Suggest going to About this Mac and it will provide the required information needed in the next step.
This link How to get old versions of macOS will need to an Apple Site where you must explore each available macOS Requirements against the Age of this computer. Then and Only then can one download and install the newer macOS. Be certain to Only use Safari to start the Download as Other may not work. Also, perform a Time Machine Backup Before attempting the upGrade.
Special Notation - Starting in Catalina and Big Sur - there is No Support for anything 32 bit and there is no workaround.