ok, so go on to the
hooboo mountain and then make your way to the hammer bros house, beside the bridge that is broken. A villager will tell you that they are out, and the bridge workers will tell you to go talk to some villagers, (this was the part i got stuck on) no matter how long you wait, talk, socialize whatever you wont be able to cross the bridge or speak to the hammer bros until you head as far down the mountain untill you meet cacklattas stuge. He will block your path with a stone that can only be broken with a hammer, go back up to the hammer bros and they will be there and tell you to go to the top of the mountain and get them a special stone, the bridge will now be repaired so make your way to the top and defeat the boss, head back down and recieve a hammer for mario and luigi.