Hi Different articles are been discussed on the same. Please refer these link and hope it will help you.
Moreover, This will be a new Hyper-V 2012 host with two Server 2012 VMs. 1 DC and 1 Exchange 2013. Late this year It will probably get a SQL Server VM too but that is down the road.
I want to migrate FSMO roles and Exchange appropriately and then decommission the SBS 2008 Server. I have a Server 2008 R2 license that will be installed on the old hardware and the unit wil be sent to a remote branch for local replication of the shared drives.