Cannot connect portable disk drive USB-C to USB MacBookPro

This question was asked before on this community but was not answered properly. I'm trying to attach an Apple portable Disk drive to my new Mac Book Pro using a USB to USB-C adaptor. I'm getting the message USB Accessory Needs Power: Connect "Apple USB SuperDrive" to a USB port on this Mac. Impossible to do so directly as the connector from the disk drive is USB. What gives?