If you're talking about the 3rd badge in Hoenn (R/S/E) then here's what you do: If you haven't already, get the rock smash HM. Search the houses south of the fence. One of them has a scientist-like guy. He will give you rock smash. Now, go do whatever with your new rock smash move! If you want to go on, go north from Mauville. You'll go through a few routes and whatnot and end up at Fallarbor. After a short excursion with Team Aqua/Magma, you can go up to Lavaridge, where the 4th gym, the fire gym, awaits you!
in veilstone
It depends which ones are you looking for. The 8th Badge is in Sootopolis, The 7th badge is in Mossdeep, The 6th Badge is in Fortree, The 5th badge Is your dad in emerald it is found at Petalburg, the 4th Badge is in Fallabore, The 3rd badge is in Mauville, The 2nd badge is in Dewford, The 1st badge is in Rustboro.
The 3rd badge.
Back in the 3rd town where your dad is hope this helps :)
Defeat the 3rd Gym Leader, Wattson, in Mauville City.
The third badge is in Goldenrod City.
in veilstone
if you are looking for the third gym badge i suggest Veilstone city.
You get your 3rd badge in Veilstone city against Maylene.
It depends which ones are you looking for. The 8th Badge is in Sootopolis, The 7th badge is in Mossdeep, The 6th Badge is in Fortree, The 5th badge Is your dad in emerald it is found at Petalburg, the 4th Badge is in Fallabore, The 3rd badge is in Mauville, The 2nd badge is in Dewford, The 1st badge is in Rustboro.
I'm pretty sure in vermillion.
you got to go to veilstone and that's where she is.
it's the 3rd badge!
The 3rd badge.
You have to wait a while and talk to her. She will give the badge to you when you talk to her.
you go the the fourth gym in pastora and battle him
Back in the 3rd town where your dad is hope this helps :)