Where can you find Strength on Pokemon FireRed?

Just head to the last portion of the Safari Zone and head south and you'll find the Warrens Gold teeth in an item ball. Go outside the Safari zone and his house will be east of the Pokemon center. Enter and give him his teeth and he'll reward you with HM 04-strength. He also has a rare candy you can now access with strength.
You find strength by going into the safarri zone and finding the wardens teeth wich you give him and he gives you strength.