From the Super Mario Wiki
Choombas Charge! is a level in the Lava Lair in the Bowser Jr.'s Journey mode of Mario & Luigi: Bowser's Inside Story + Bowser Jr.'s Journey.
The level contains three battles. The first battle has three Choombas and two Chuboombas at the front, two Bomb Boos in the middle, and a Bomb Boo first officer and Choomba captain at the back. The second battle has two Chuboombas and one Choomba at the front, four Bomb Boos in the middle, and a Choomba first officer and captain at the back. The final battle contains two Chuboombas, two Choombas, four Bomb Boos, no first officer and a Choomba captain.