After saving Princess Peach from Bowser's forced marriage during the Main Story, your main objective in the Post Game is ultimately completing the goal of finding and obtaining all 999 Power Moons. Within all the Kingdoms, there are exactly 556 Base Power Moons that you can find with Mario. There are an additional 324 Power Moons that can be obtained through Archivist Toadette and the Moon Rocks found in all Kingdoms. From there, the last 119 Power Moons can be purchased from any and all Crazy Cap Stores.