How do youn get the third appa andventure on avatar burning earth?

It seems you're asking about the third part of the Avatar: The Last Airbender series "The Legend of Korra", specifically the "Burning Earth" book. However, "Burning Earth" is the second book of the series.

The third book is called "Change", and there is no separate part or "adventure" within it.

To access "Change", you can:

* Stream it on services like Netflix or Paramount+ (depending on your region).

* Purchase it on DVD or Blu-ray.

* Find it on digital platforms like Amazon Prime Video or iTunes.

Let me know if you have any other questions about the Avatar series!