I decided to use WMI to solve this problem but I found that it's impossible to get the drive letter of the specified USB device via Win32_USBHub class.
I can find the drive with the following wmic command: wmic logicaldisk where VolumeName='USB-BACKUP' get deviceid |find /v DeviceID it returns Q: and that ...
USB driver for MIC-3318. 2004-12-13 Driver Document No.1-36566193. Related OS: Device Driver, Win2000, Win98, WinXP, Windows ME. Related Product: MIC-3318.