I'm not Sure, I think like the xbox 360, the One might need some Hard Drive partition reader also but don't think any are available but they is for 360 if that could be used.
I try formatting a 128GB USB Drive yesterday, All i got was videos/music on the xbox one, No games are saves transfer's sadly, Maybe it might for a harddrive, Maybe take out a old 360 one from its case as it has a cable and just a mini Sata drive with xbox 360 data formatted on it.
The tool used for 360 was called Horizon, It may on anti virus programs have little false positive.
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I would love to see the Vantage tool re-fixed with Xbox Saves, And not PC only now.
The no saves with Vanage is just a random issue, If you keep trying login in out / refreshing, you will get through, also tip make the game you play a lot be first on Vantage list, If ie its listed as a first game more likey the saves will show up there, and not the next game on the list.
But not likely to be now, And Vantage guy Removed this function for xbox one, And made it PC only, down to people selling game saves / editors est, rather then sharing, real shame but hope he comes too and adds it back into vantage tool.