
Explanation/Reference:
Note:
Step 1: Install Azure Active Directory Synchronization Services (AAD Sync).
AADSync will for most customers be relevant when a new feature is required that is only available in AADSync.
Step 2-3: Import and Synchronize
(Step 2)Select Connectors, and select the first Connector with the type Active Directory Domain

Services. Click on Run, select Full import, and OK. Do this for all Connectors of this type.
Select the Connector with type Windows Azure Active Directory (Microsoft). Click on Run, select Full

import, and OK.
(Step 3) Make sure Connectors is still selected and for each Connector with type Active Directory

Domain Services, click Run, select Delta Synchronization, and OK.
Select the Connector with type Windows Azure Active Directory (Microsoft). Click Run, select Delta

Synchronization, and then OK.
Step 4: Verify
Start a cmd prompt and go to %Program Files%\Microsoft Azure AD Sync\bin

Run: csexport <name of Connector> %temp%\export.xml /f:x

Etc.
Reference: Moving from DirSync or FIM to Azure Active Directory Sync
https://msdn.microsoft.com/en-us/library/azure/dn783462.aspx