In pokemon firered, how do i get to the cave that leads to lavender town?

im stuck after the 3rd gym and i dont know where to go! please help me!

In pokemon firered, how do i get to the cave that leads to lavender town?
you go to cerulean city and through the house that was wrecked. now immediately go right and cut down the tree there. there will be a few trainers so be ready for them. at the end, you will see a patch of grass where you will be able to catch voltorb and something else (can't remember) go down from there, and there will be this random pokemon center. yuer gonna need flash for this cave for that, go through diglett's cave and talk to professer oak's aide. go through the tunnel and you'll be in lavender town.
Reply:Okay, so after you've battled Lt. Surge, you go through Route 11, then through Route 9 and that takes you to the Rock Tunnel. After that there's Route 8 and then you get to Celadon City. From there you have to beat the Rocket Base before you can continue on to Lavendar Town.