Here’s a document straight from Microsoft on the migration plans: http://download.microsoft.com/download/a/9/4/a94c5f56-f7b5-4ec8-bcaa-1eadf84c4e3f/V3MigGuide.doc
Using ADMT is easy but it will be quit difficult.
I think for this we can use MOVE TREE Command
Please find the link below for the same
Since for moving a Object between a single domain we can go for the command movetree.exe