I recently cleared this exam by preparing the topics listed in the  "prerequisites", in the below link. The exam questions were based on these topics.

https://academy.databricks.com/exam/databricks-certified-professional-data-scientist

you can also enrol for the "preparation" courses listed in above link.

In addition, I also used this book for preparing "Hands-On Machine Learning with Scikit-Learn and TensorFlow_ Concepts, Tools, and Techniques to Build Intelligent Systems".

Good luck !!