update apple mac

You need to provide more information. Click on the Apple menu in the top left corner of the menubar and then select about this mac. There you will find the 2 pieces of information we need: Your computer's model and year (for example MacBook Air mid 2014) and the OS version (for example Mojave version 10.14.6)

To expand on stedman1's answer, there are no more updates to Yosemite, you have the most recent version. You need to upgrade to a newer version of the Mac OS. Mojave is the current OS version you'll upgrade to.

Please see: Upgrade to macOS Mojave - Official Apple Support