Picked up modem and it didn’t come with an ethernet or coax cable

I just picked up my modem this morning and when I got to my new place and wanted to install it I couldn’t find the coax cable. I called support and I was told that the cable should be found in my apartment and that if my apartment doesn’t have it a technician would have to come and I would have to pay $100 dollars. I checked an Xfinity article and it mentions that the installation kit includes a Coax cable (which is the only thing I need to make this work). How can I get one?