The CPB200 course is the final step before you can sit for the Google Cloud Certified Professional - Data Engineer certification. Please refer to the following page for more details https://cloud.google.com/certification/data-engineer?
You can get the certification following the process:
Step 1: Complete all the required trainings. Please
Step 2: Register for exam at: https://webassessor.com/wa.do?page=publicHome&branding=GOOGLECLOUD
Step 3: Google informs the participant if they have passed the examination and receive the certification
Certification and examination related FAQs are available at https://cloud.google.com/certification/faqs/#0