Because the Mission Zero game has not yet been released, you will not be able to locate it in the official app store of any device, whether it the iTunes App Store for Apple iOS, the Google Play Store for Android, or the Windows App Store for personal computers. Visit the official website for the Mission Zero game, which can be found at https://www.missionzero.game/, in order to pre-register for the game. This is the only way to do so.