Thank you for reaching out to us.
Refer to this article https://learn.microsoft.com/en-us/azure/active-directory/hybrid/migrate-from-federation-to-cloud-authentication for detailed documentation on migration from federate to cloud authentication.
To answer next query which is better password hash sync or pass through authentication - depends on what organization wants, refer to this article https://learn.microsoft.com/en-us/azure/active-directory/hybrid/choose-ad-authn which helps you decide between password hash sync or pass through authentication.
Let me know if you have any questions.
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