If I cut and paste a file/folder from my external storage device to my PC, and both devices get disconnected during the process of transfer, how do I retrieve the damaged file?

If you did a cut operation and it did not complete, non transferred files should still be on source device.I suggest to never do cut/paste with multiple targets between different devices: better use copy/paste and then delete when operation is correctly completed.Unfortunalely operating system interfaces are not consistent with these operations from graphical interface, especially when operating on large files or large numbers of file/folders. A single error can interrupt the copy without any simple recovery options. On windows it is better use robocopy command line tools which is far more reliable and also produces a good log. Robocopy can also be run several times to complete an interrupted operation.