You have to first catch a Gible, which you then evolve into a Gabite which then evolves into a Garchomp at level 48. You can find Gible under the cycling road to the North of Oreburg city. Then you cut down the trees, and go to the far side. There should be a cave entrance hidden under the bridge.
either get a gible from wayward cave (route 206) or a gabite off victory road, then level it up to lv48.
You either cheat,trade.or level up Gible/Gabite.
Garchomp cannot learn Giga Impact from leveling up in Pokemon Platinum. Garchomp can learn Giga Impact from the TM that teaches it which is TM68.
Gallade is. Garchomp and Gallade can learn Dark Type moves, and Gyrados can learn Ice.
garchomp
if there levels are at least 65, pretty good[have you caught giratina, dialga, and palkia yet?]
Three of your pokémon are weak to Ground, you should try to fix that.
The 111th Pokemon on Platinum is Garchomp.
in batman city
Garchomp cannot learn Giga Impact from leveling up in Pokemon Platinum. Garchomp can learn Giga Impact from the TM that teaches it which is TM68.
Cynthia elite 4
You can't. You need to evolve Gabite.
Gabite evolves into Garchomp at level 48.
diamond and pearl spirttomb garchomp roserade gastrodon milotic and lucario platinum spirttomb garchomp roserade lucario milotic and togekiss
Cynthia has: Spiritomb Lucario Garchomp Togekiss Milotic roserade
Level 78
If You Just Want To See A Garchomp For Your PokeDex, Champion Cynthia has one. If You Want To Catch One You Have To Evolve A Gible Into Gabite, Then Gabite Evolves Into Garchomp.
On the real fire red that is impossible, as garchomp only exists in pearl, diamond, platinum, heartgold, and soulsilver. Firered only goes up to #386 Deoxys
catch a gabite on victory road and level it up to lv48 good luck :)