We have SmuggLr as a tool that may help you. You can see full details about it here: http://www.smugglr.com/
At the bottom of that page there's a link to click on for directions for either Windows or Mac.
If you are wanting to migrate photos from Amazon Drive, Google Photos, Dropbox or Flickr, check out the details here on our upload help page that talk about uploading right from our upload tool within SmugMug from those services. Available here: http://help.smugmug.com/customer/portal/articles/1386737?b_id=1644