After completing the main story, you must speak to the Toad in the Mushroom Kingdom, in front of the castle. He will tell you that Princess Peach has gone on a world tour. Once you have spoken to her in every world, you can find her again in the Moon Kingdom.
Cap Kingdom
To do this, Mario must speak to Peach, who is standing on the way to the Top-Hat Tower, after the Crazy Cap shop.
Cascade Kingdom
Above the Fossil Falls you will find Peach, who will give you another moon.
Sand Kingdom
Search on the floating, upside-down pyramid. You should be able to get there quickly using the power line.
Lake Kingdom
Princess Peach can be found at the spot where you fought the Broodals after the main story.
Wooded Kingdom
Peach is on the observation deck and gives Mario a Power Moon if he talks to her.
Metro Kingdom
You can find Peach on the roof of the building south of the “ Open Air Cafe “ checkpoint.
Snow Kingdom
You can find Peach in the central room of the Shiverfield settlement.
Seaside Kingdom
On the roof of the glass palace you can find Princess Peach with another Power Moon.
Luncheon Kingdom
The princess has made herself comfortable in the city center. You can find her at the eastern shop.
Bowser’s Kingdom
At the Bowser’s Kingdom shop, you’ll meet Peach, who will give you another Power Moon.
Moon Kingdom
After you have found Peach in each world, she is at the very end on the bell tower and gives you a Power Moon.
Mushroom Kingdom
After you’ve found Peach in every world, she’ll be on the bell tower in Moon Kingdom at the very end. Afterwards, you can find her on the balcony in Mushroom Kingdom.