You'll earn this on your way to getting 170 stars.
You don't need to get 3 stars on every level to get 170 stars (there's 60 levels), so I'd advise to first clear all the levels with however many stars you get.
Also, be sure to buy the highest multiplier upgrade to boost your points as much as possible, which is why it also helps to just play through the game first, to unlock those later upgrades.
Then, you can start working on improving your scores to get to 170 stars, once you find out how many you need. Obviously the earlier levels are easier to get stars in, so you want to start from the bottom.
Here are screenshots of my scores, to give you a frame of reference to shoot for, when going for the stars. I can't tell you how many points you need to get 3 stars on each level, but if you shoot for these scores, you'll obviously get 3 stars.