You get the 7th badge on Cinnabar Island. In order to get there you will need to surf. To find out exactly where Cinnabar Island is, look at your town map.
Cinnabar Island's gym focuses on fire types so it will be a lot easier if you have a Pokemon that knows a water or ground move.
In the gym, you will have to go to a certain machine in each room. This machine will ask you a question. If you answer it correctly, you get to move on to the next room. If you get it wrong, you will need to battle a trainer and then you can go to the next room.
Chat with our AI personalities
It is not possible to get a ninth badge in Pokemon FireRed. You can only get eight badges in Pokemon FireRed.
Fight the seventh gym on Cinnabar Island. Then fight the eighth gym at Virirdian City.
GET THE LAST BADGE......
The 7th badge.
island? the fourth badge is in celadon