You can't. At least, not easily.
Phones do not connect as Mass Storage devices. They connect, instead, via the Media Transfer Protocol. They don't appear as storage drives, but instead are interfaced via a different protocol. This is out of reach of the Command Prompt in general.
The only way to get this, I think, would be to root the phone and install some sort of software designed to allow the phone to be exposed as a Mass storage device instead of an MTP device.
Maybe it can be manipulated directly via Powershell?