You have to beat the game again to get the extra level and the last star to make 121 stars. The Dreadnought 100 coins level, is alot of lining up mario with the coins or when your hanging upside down, is lining up mario with the shadows of the coins. The biggest thing is to see where all the coins are and where to line Mario up at at end section after hoping across. Trying not to move so much when collecting coins, once you're lined up, just collect the coins. If I remember right near the end isn't there some coins really high above the electric gate. If so, then you have to sacrifice a level of power or two to get those tricky ones.