Where do you get the protecter in FireRed?

You can't get a Protector in FireRed.

The Protector is an item introduced in Generation IV (Diamond, Pearl, Platinum). It's a held item that prevents a Pokémon from being affected by a status condition, such as paralysis, sleep, poison, or burn.

FireRed is a Generation III game, so it doesn't include items introduced in later generations.