how can i get my apple macOS software up to date

Hi,

iOS is for iPhones.

To upgrade your Mac, go to the Apple Menu > About This Mac to see exactly which Mac you have, then find out if it is compatible with a newer OS here: How to get old versions of macOS - Apple Support or here: How to upgrade to macOS Monterey - Apple Support

Before upgrading, backup, check apps and peripherals for compatibility with whichever OS you decide to upgrade to.

Catalina, Big Sur and Monterey will not run 32 bit apps, so download Go64 and scan your Mac to see which of your apps are 32 bit and will need to be upgraded/replaced: https://www.stclairsoft.com/Go64/

Some apps may be 64 bit but still not run on a particular OS; you can check them out here: https://roaringapps.com/apps

iOS 15 is for iPhones.

Your MacBook can be updated to Big Sur 11.6.7.