In order to persuade him, you must first collect the seven other Kanto Gym Badges. To earn the seventh, you need to track down the Gym Leader of the displaced Cinnabar Gym. With the building destroyed, Blaine was forced to relocate to a cave in the Seafoam Islands to the east.
Correspondingly, how do you get misty to appear in soul silver?
You find that by going in misty's gym in Cerulean City (but you HAVE to talk to the guy in the power plant first) in the gym you'll find a team rocket member and he runs out, chase him north of Cerulean and then he battles you and tells you where the power plant part is.
Where is the power plant in soul silver?
Conveniently, Cerulean City is immediately west of the Power Plant, so you can leave through the City's western exit to reach Route 9. You might want to heal and grab a Cut slave at the Pokemon Center before you go. Route 9 connects Cerulean City and Route 10, which is where the Power Plant and Rock Tunnel are located.
Where is Misty?
Three years later, in Pokémon Gold, Silver, Crystal, HeartGold, and SoulSilver, Misty remains the Gym Leader of the Cerulean Gym, which can be challenged once the problem at the Kanto Power Plant has been fixed. Initially, she cannot be found in the Gym.