During the Main Story, Mario and Cappy will have to find Power Moons in order to power up the Odyssey to travel from kingdom to kingdom. After the Main Story is completed, Mario can find and obtain additional Power Moons in order to unlock new Kingdoms and Costumes. In The Darker Side, there is only 1 Power Moon that Mario can find and obtain.
Darker Side Power Moons & Mission Titles
Darker Side Power Moon 01 - Long Journey's End