In this game, there are a total of 150 unique pokemon which you can catch and use in the tournaments, You can find these Pokemon while traveling on the Route or in different towns.
To catch a Pokemon in the pokemon fire red game first you need to buy a Poke ball which you can buy from PokéMart in this game, After getting the Poke balls you can find the Pokemons while traveling in the grasses,
Once you find a Pokemon you need to knock them out so that you can easily catch them using your Poke balls.