i think its 3,4, or 5 sorry its no help
the boulder badge from brock
The fifth Gym Leader in Pokemon LeafGreen is Koga, the leader of Fuschia City's Gym. He specializes in Poison-type Pokemon and hands out the Soul Badge.
The sixth gym badge (the Marsh badge) is located at Saffron City's gym. It is in Gym Leader Sabrina's possession, so you have to defeat her to obtain it.
in Viridian city. the one that was locked.
Open the door and challenge the gym leader.
Beat Giovanni at viridian city's gym.
In cerulean cities gym you must beat the leader misty to get the cascade badge.
the one you get from the gym in fuschia city.
Get the 7th or 8th gym badge, and its in the Power Plant.
You have to defeat Erika.
You can get it from the Viridian City GYM. Good Luck!
Its in Viridian City, the Earth Badge, vs. Giovanni