Hi,
create volumes and shares on the netapp and then go for
robocopy.exe "\\source\share" "\\dest\share" /MIR /SEC /R:1 /W:1 /ETA
You can run that command multiple times for delta transfers. When moving huge chunks pipe the output to a file with /L:logfile to speed up the process.
Google around a bit for robocopy, there are even gui tools available.
If you have very very old and chaotic structures, securecopy is worth a try but it costs per migration.
Good luck!