I'm following this tutorial to create a Turn Based Multiplayer game: https://developers.google.com/games/services/console/enabling
Under the Specify client ID settings section, they say to run:
keytool -list -keystore [path-to-debug-keystore]
That's fine because they also mention the location of the debug keystore: "On Windows, the debug keystore can be found at C:\Users[USERNAME].android\debug.keystore."
They also say to run this command:
keytool -list -keystore [path-to-production-keystore]
But they don't mention where the release/production keystore is.
...where is it?
You generate the production key yourself. Read Sign Your App in the android developer documentation.