Penny’s Big Breakaway has 11 worlds in the main story, which is the clearest count available from the sources I found.

Quick Scoop

  • The game’s campaign is organized around 11 total worlds.
  • Reviews also mention bonus stages and boss fights, but those are separate from the main world count.

Item| Count
---|---
Main worlds| 11 1112

TL;DR: 11 levels/worlds in the main story.