Jupiter, I promise, I'll always know where to find you.
A car drives into the Jack's family's property, and for the family, this car contains their new family member, Jupiter.
Jupiter comes out of the car and meets the family. She is first introduced to Jack. Just like Joseph, Jupiter calls Jack "Jackie", and Jack promises her that he will always know where she is, just like Joseph.
This scene is an extremely significant portion of the novel. It is a resolution that represents the making of a new family, and pursuing hope and dreams.