Hi,
To receive a copy of the Microsoft Dynamics CRM Online SQL database, contact Live Customer Service by calling 1-877-CRM-CHOICE (1-877-276-2464) Monday-Friday, 8:00 A.M.-8:00 P.M. Central Time (UTC-6) in the U.S. and in Canada.
As billing have the migration tool they will provide you the back up of entire organization .
Below Link include the entire Steps to migrate from Microsoft Dynamics CRM Online to Microsoft Dynamics CRM 2011 On-Premises
rc.crm.dynamics.com/.../online_to_onpremise_migration.aspx
Hope this should help you.
Thank You.