Software Compatibility for early 2009 Mac

An Early 2008 through mid 2009 MacBook Pro can be upgraded to El Capitan 10.11.6 but no later version. See: How to get old versions of macOS - Apple Support

@FoxFifth is correct. Here is an article which shows the compatibility of each macOS and Apple hardware which is really useful:

https://eshop.macsales.com/guides/Mac_OS_X_Compatibility