My National Pokédex on my Pokemon Fire Red only goes up to 250. Is it possible for it to go up to 386?

Question

I see Pokédex on fire red go up to 386. But my one goes up only to 250. Why?

Answer 1

The problem is: You don't have the entire Hoenn Pokédex.

Since your NatDex only goes to Ho-Oh, to unlock a "third" part of the Natdex is simply getting a Hoenn Pokémon by trading with the Hoenn games (RSE).