Unable to connect with current cable to MacBookPro laptop

Purchased new MacBookPro and the plug/connection cable does not connect to laptop. Where do I get the type of plug needed to attach to laptop? From WD or Apple? Requested form asked for S/N and it wouldn’t accept my S/N???

Do you need my email address to talk to me ? This is beginning to be a hassle. I purchased this to work not sit in a corner. I am a busy business person and this is causing me much delay.