You can practice this by setting up a small lab in *Azure*:

1. Create a VM with Windows Server + AD DS.

2. Add another VM with Exchange 2010.

3. Install Azure AD Connect to sync with Office 365.

4. Use the Exchange Admin Center or PowerShell to migrate a few test mailboxes.

Microsoft has step-by-step docs you can follow:

* Hybrid deployment prerequisites - (https://learn.microsoft.com/en-us/exchange/exchange-hybrid)

* Migrate Exchange 2010 mailboxes - (https://learn.microsoft.com/en-us/exchange/mailbox-migration/office-365-migration-best-practices)

For production projects, some admins use migration tools (e.g. Kernel Office 365 Migration Software) to simplify mailbox moves, but for practice, it’s best to stick with Microsoft’s native guides so you learn the process.