You need to find a ROM file of Pokémon FireRed (U) v1.0 . The filename usually includes "Squirrels".
Here is a comprehensive guide to what the "Squirrels" dump is, why it became the industry standard, and how it powers modern Pokémon ROM hacking. What is "1636 Pokemon Fire Red Squirrels"? 1636 Pokemon Fire Red Squirrels
If you have this file, you are likely looking to patch it into one of these popular fan games: You need to find a ROM file of Pokémon FireRed (U) v1
While the ROM file itself falls into a legal gray area regarding copyright law and intellectual property, its numbering convention remains shorthand in the emulation community for quality, stability, and compatibility. why it became the industry standard
Practical notes