Before I would do that; I would immediately turn off your computer by shutting it down from the W10 Start Menu as Neem illustrated.
Then remove your flash drive from that computer by physically unplugging it from the USB port. Then take it to a different computer preferably running W10 also. If not available, you can test the integrity of the flash drive on any other computer running Vista/W7/W8 by plugging it into it's USB port and see if you can read the file directory (see if your files and folders are there).
On your Post #13 you do not want to answer "Y" to that opened handles question, since dismounting the volume can corrupt the MFT (Master File Table) or index on that drive and it will be very near impossible to...