Porting numbers to Zoom without a BTN

Hello:

I am a new customer to Zoom Phone and plan to port numbers to Zoom. The Porting Form asks for a BTN. Our current phone bill doesn't show a BTN. I've asked my provider (Century Link/Lumen) how to obtain one if it isn't listed. Their reply is that I may just have to skip that step in the process. Not sure how to proceed.

Thanks!