What episode is Sailor Moon on a big rock covered with pink floweres?

You're likely thinking of Episode 54, "The Flower of Evil Blooms", from the original Sailor Moon anime series. In this episode, Sailor Moon and the Sailor Scouts find themselves on a large, pink-flowered rock in the middle of a vast, empty landscape. This is the home of the "Flower of Evil", a powerful monster created by the Dark Kingdom.

Let me know if you have any other Sailor Moon questions! 😊