There is no special way to do that, but there are some points to consider
- you need to have a root volume for the vfiler and then you can create it "empty" with only the root volume
- you have to do the CIFS setup of the new vfiler
- you can only assign the volume with the data to the vfiler but not the shares, they have to be recreated on the vfiler
- if you use local users or groups, you have to perform a front end migration using a tool like secure copy, because the the vfiler has its own SID, users and groups. This means as well, you need double the space to be able to copy the date from the vfiler0 to a new empty volume that belongs to the vfiler.
Thats about it, with those steps you should be fine for your migration.