I’m curious, can you elaborate why you need this connector?

To answer your questions, those two USB A connectors are for power and data transfer, separately. But if you got a 3.5" drive, you’re going to need that external 12V power supply anyway.

You can plug the data USB connector into the same PC to manage the files, but you can also put it in a different PC to transfer files between two devices.

You can also use a power bank for the USB A power connector, but this will again only work with the 2.5" drives.