you must fight the team rocket leader, giovanni, again. (he's the gym leader.)
go to the celadon city gym
saffron city (psychic type gym leader)
there is no gym leader in lavender town
None he's not in firered.
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.
Pewter City.
Viridian City.
The gym leader after Misty is Lt. Surge. He is the gym leader of Vermilion City, specializing in Electric-type Pokemon.
You go to saffron city
In the 4th gym ! After you beaten the gym leader in saffron city!!
In the viridian city. The gym leader is the boss of team roket
he is in the gym in vermillion city on fire red and/or leaf green