How to migrate Windows Server 2008 R2 from Enterprise to Standard?

Question

Windows Server

Raise Hyper V on the server, it has an Enterprise virtual machine.
you need to migrate Windows Server 2008 R2 from Enterprise to Standard.

Answer 1

Downgrade as such does not exist, so the right solution would be to raise pure Win2008R2 Standard on the same Hyper-V and migrate roles / transfer data.
What is the reason for the transfer and what roles are raised on the Enterprise version?