App Store
How do I get the App Store on my Apple watch
Apple Watch, watchOS 4
The App Store app is part of watchOS, it should be there.
You can also access the Watch App Store from the Watch app on your iPhone in the Discover tab.
M1 Mac mini, macOS 11.2.3; Watch, series 5 GPS/cellular, watchOS 7.3.2; iPad Pro 2nd Gen, iPadOS 14.4.1; iPad Air 2, iPadOS 14.4.1; iPhone 12 Pro, iOS 14.4.1; TV 4th Gen, tvOS 14.; HomePods, audioOS 14.4.1 and Airport Express w/ Airplay 2