Hi,
The method I usually use is Windows Robocopy. If you create a main share folder on the filer then you can use Robocopy to migrate the files to it over the LAN.
Robocopy is basically a file copying script but it does have a GUI front-end. You can also choose to keep the same file permissions, security etc which is very handy when using AD.
You can download Robocopy from the Microsoft site.