URL for SQL Server

Dear All,

I've implemented SAP 9.0 PL 05 in customer place , Initially I've used SQL Server Express Edition.

Now our customer has ready to Buy SQL Licence.

1) How I can Download\ activate licence for SQL Server 2008 r2

2) How to migrate DB from Existing Instance to new Instance.

Knowledge about SQL Server would be very helpful.

Thanks & Regards

M G