I Need a Bomb (バクダンの作り方, Bakudan no Tsukurikate, lit. How to Make a Bomb) is an event in Tomba!.
Find a bomb that can be used to break open the big rusty iron door.
In the Lumberjack Factory, talk to the man in green to activate the event. He will tell Tomba about a bomb he made a long time ago. Because of its dangerousness, he hid it in the highest palm tree in the Masakari Jungle.
Go to the Masakari Jungle and climb the tall palm tree to the left when you exit the door to the Y-crossing. Climb all the way up to the top to find the bomb on the tree's left side and clear the event.