Feebas evolves into Milotic when it reaches level 30 and has a Beauty Contest rating of at least 3 hearts.
Here's how to get those hearts:
1. Obtain a Feebas: Feebas can be found in various locations in the Pokémon games, typically in specific bodies of water.
2. Use the Contest Spectacular feature: You can find this feature in specific towns in the games, where you can compete in beauty contests.
3. Earn hearts: Based on Feebas' stats and how you dress it up, it will earn hearts in the contest.
4. Reach 3 hearts: Once you reach 3 hearts, your Feebas can evolve into Milotic at level 30.
Remember, it's not about winning contests, but about achieving a high enough Beauty Contest rating.