canalave city...
4th gym
The Gym Leader that allows you to use the HM move Strength in Pokemon FireRed is Erika. Erika is the Gym Leader of Celadon City and is the 4th Gym Leader the player faces.
Veilstone.
You will be able to use HM04 Strength outside of battle after you defeat the 6th gym which is in Canalave City.
In Pokemon Red/Blue/Yellow and Pokemon FireRed/LeafGreen, the Celadon City Gym Badge is required to use Strength. Gym Leader Erika holds this badge.In Pokemon Gold/Silver/Crystal and Pokemon HeartGold/SoulSilver, the Goldenrod City Gym Badge is required to use Strength. Gym Leader Whitney holds this badge.In Pokemon Ruby/Sapphire/Emerald, the Lavaridge Town Gym Badge is required to use Strength. Gym Leader Flannery holds this badge.In Pokemon Diamond/Pearl/Platinum, the Canalave City Gym Badge is required to use Strength. Gym Leader Byron holds this badge.In Pokemon Black/White and Pokemon Black 2/White 2, Gym Badges are not required to use HMs.
canalave city gym
By defeating the the fourth gym leader
Veilstone Gym.
you use strength. you get strength on route 42. you can use it in the wild after you beat the goldenrod city gym.
get the mind badge at the canalave gym in canalave city
you need to beat flannery at the gym in lavaridge town
The mine badge.
well u have to had your forth gym badge.