* Hidden Power is determined by IVs: In FireRed, the type of Hidden Power is determined by the Individual Values (IVs) of your Eevee. These values are randomly generated when the Eevee is created and are hidden from the player.
* No way to check IVs: There's no in-game method to check the IVs of your Pokemon in FireRed.
* Limited type possibilities: In FireRed, Hidden Power can only be one of 15 types: Normal, Fighting, Flying, Poison, Ground, Rock, Bug, Ghost, Steel, Fire, Water, Grass, Electric, Psychic, and Ice.
To find out the Hidden Power type of your Eevee in FireRed, you'll need to:
1. Train your Eevee to level 30: Hidden Power learns at level 30, allowing you to see its type.
2. Use a move tutor: If you're playing on a cartridge with a hacked move tutor, you might be able to teach your Eevee a move that reveals its Hidden Power type.
It's a matter of luck! You can't choose the Hidden Power type you want in FireRed. You have to rely on the randomly generated IVs of your Eevee.