* Golem is a Gen I Pokemon: FireRed is a remake of the original Pokemon Red and Blue games. While it includes all the Pokemon from those generations, it doesn't have Pokemon introduced later in subsequent generations. Golem is a Gen I Pokemon, so it's in FireRed.
* Golem is a traded evolution: You can't find a Golem in the wild in FireRed. It evolves from Geodude, which evolves into Graveler, and then finally Golem. However, you need to trade a Graveler to evolve it into Golem.
So, you can't find a Golem in FireRed, but you can obtain one through trading.