How can you find jirachu on Pokemon FireRed?
You cannot find Jirachi (there is no Jirachu) in Pokémon
FireRed legitimately without a cheating device. One way is to trade
with a Ruby or Sapphire version that was able to collect one when
it was being distributed. It, along with the other event legendary
Pokémon, is still being distributed in the more recent versions of
the game, though not very often.