You’re welcome!
And yes, you have to repeatedly play levels. And as you complete the Missions, new ones appear, so then you need to complete more levels again.
That thread I linked above (Season 2 Missions Advice (Enemies, Bosses and Special Stages)) attempted to recommend an efficient way to complete multiple missions at once.
But no matter how you do it, it requires a fair amount of replaying of levels.
The Mission in your screenshot is actually a second round of special stages. The first only requires beating 50 stages:
