If you want to update apps downloaded from the App Store, use the App Store to get updates.If Software Update says that your Mac is up to date, then macOS and all of the apps it installs are up to date, including Safari, Messages, Mail, Music, Photos, FaceTime, Calendar, and Books.
If you're having difficulty finding or installing updates: Learn about the latest macOS upgrade, or about old versions of macOS that are still available. Learn about macOS Big Sur updates, for example.