When you use PicBackMan to migrate photos from Picasa/Google Photos to your Flickr account, it does not make any change to your album/folder structure. They all will be migrated as it is. The name of the albums will be same and it will also include the same set of photos. Every Google Photos album will be migrated as a Flickr photo set.
PicBackMan is a free photo/video uploader that helps you to keep your memories backed up to your favorite online services.
Users in 130+ countries have backed up.
... an excellent job of uploading more then 300GB of photos to 2 different services