Expansion Desktop Drive recover of files saved in Vista

I backed up my files on Seagate Expansion desktop drive 2 TB with Vista operating prior to upgrading to Window 8.1
When I tried to retrieve my documents and pictures into Window 8.1 very few files are there and only a few documents and they are at least a year old. I have 10 or more backups on the expansion drive.
I have search Seagate with little help. I have thought maybe I should find a Vista machine and see if the files are there.
It appears to backup with 8.1 but I have not check specifically for documents in the 8.1 back up.
Any thought on getting all my document and pictures off the external hard drive back on the 8.1?

The operating system version you used should not matter, what does matter is HOW you backed up the files. Did you simply use a file manager and drag-and-drop the files to the drive? Or did you use a backup app -- and if so, which one?

If you only did the drag-and-drop you may have to resort to data recovery apps to get the files back. One such free one is "recuva".

I did not drag and drop so there must have been an app as it would auto back up on Sunday night if the computer was running. I do not recall loading any app. E-mail reply for Seagate said it did not come with software. As best I can remember I just did a quick start up with a menu that set the auto run times etc. So where did the app come from?
I did jot down all the programs in the Vista Program file before I up dated to 8.1 and the most likely name I see is "Windows portable device" Would that have been the one?
Of course all those programs were wiped with the update to 8.1
I can see the backup files for the various back up dates but can't find or transfer the document files or folders with 8.1 Are there any suggestions to try and get them from the external hard drive?

If you turn on file extensions in Windows explorer, you should then make a note of what is used by the backup files. That will help us figure out what app wrote the backups.