If you are satisfied with the existing structure on your file server, it is even easier.
This is the easy way for you to move your documents in a controlled manner and start working with documents in office 365.
In MetaShare, you set up one or more workspaces as archived workspaces. You migrate your documents to these workspaces using SharePoint Migration Tool (SPMT), keeping the same structure as you had on your file server. All the migrated documents will maintain their existing file properties (file name, created, modified, created by & modified by).
An option is to also maintain any unique permissions that were set on folders and/or documents. In the archived workspaces users will be able to navigate and search for documents in the same structure as they were stored on the file server. In these archive workspaces, the permissions are restricted to only allow users to find, read and to move documents into new active workspaces with more metadata logic.
After a period of time, the important documents in your archive workspaces have gradually been moved into new active workspaces. Decide then if you are going to delete the archive workspaces or keep the workspace as just an archive.
Of course, this is described in detail when you activate and start working with MetaShare.