How do you get a slith scope in Pokemon FireRed?

You can't get a Slith Scope in Pokemon FireRed. This item is exclusive to Pokemon Ruby and Sapphire, and later games in the Hoenn region.

Here's why:

* Game-Specific Items: Many items in Pokemon games are specific to certain versions. This helps create a unique experience for players of different versions and encourages trading.

* Slith Scope's Purpose: The Slith Scope is primarily used to evolve certain Pokemon found in the Hoenn region, like Feebas. These Pokemon are not available in FireRed.

If you're looking to catch and evolve Pokemon like Feebas, you'll need to play a game in the Hoenn region, like Ruby, Sapphire, Emerald, Omega Ruby, or Alpha Sapphire.