Merry Meadow is one of the locations that will not be readily available for you at the start of Hello Kitty Island Adventure. In order to unlock it, you'll need to complete several quests that only become available when you've raised your friendship with Pompompurin and My Melody. At the start of unlocking Merry Meadow in Island Adventure, you'll only have access to the Merry Meadows Fields. To reach the other four areas, you're going to need to grow special beanstalks from Giant Seeds.