Read through this whole thread ... click here, it might help ...
But if you want to to this in order to use the drive on a Mac, it would be better to do it via the Mac.
Or - why do you want to reformat to a very old format like FAT??
Surface Pro (2017) vs Surface Pro 4
20 groundbreaking 3D animation technologies coming to Siggraph 2017
iPad Pro 12.9 vs Surface Pro 5
Synology invites you to visit them at Insomnia on 26th – 29th August. Book your tickets now and visit Synology.