What was Milo's quest?

Milo's quest in "The Phantom Tollbooth" by Norton Juster is a journey of discovery and adventure. He travels to the fantastical Kingdom of Dictionopolis and Digitopolis, seeking to rescue the princesses Rhyme and Reason, who have been imprisoned. Throughout his journey, Milo learns the importance of knowledge, curiOSity, and the value of Words and numbers, ultimately transforming from a bored, apathetic boy into a more engaged and thoughtful individual.