1 star: 50000 points
2 stars: 75000 points
3 stars: 100000 points
You have to get rid of the bomb in the middle in 10 moves or less, so take out some spinners and pillage the white blocks to get to it. Once it is gone, then keep on trucking as fast as you can to hit 50,000 points, you really need some help points wise, the bombs are worth 3,000 each, so grab them when you can as they will drop in from time to time.
Patricia Frederick’s Tips on Candy Crush Level 121
Work the bottom corner of either side to allow the bomb to drop into the playing field—it’s easier to remove. Then take out the bombs and make as many striped or wrapped candies as possible.