i can't find the software update icon in my system preferences

Back up your data, check your applications for compatibility, and depending on which MacBook Pro model you have, click on Mojave, Catalina, or Big Sur. It needs to be a 2012 or newer one to run a newer OS.

They're full-version upgrades and won't appear in the Updates list.

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System Preferences > App Store

Click App Store and then Updates.