i can't find software update on my Mac

I don't have exactly that version available to confirm, but:

in 10.9 Mavericks, the software update choice on the  menu tales you to the Mac App Store, with the Updates pane selected for you.

in 10.13 High Sierra, there is no 'Software Update' choice on the Apple menu OR inside System Preferences. The (Software Update) button inside 'About This Mac' takes you to the Mac App Store.

so I suggest you launch the Mac App Store, and look on the Updates pane.

MacOS 10.12 Sierra

¿did you look on the Apple menu?