You may have been asked to find your User ID (also referred to as your Referral ID) for customer support issues. Finding it is easy!
On the web:
Login and go to https://www.binance.us/en/usercenter/dashboard/overview and you'll see your User ID next your email address at the top of the page. To access this page from the homescreen: 
On the mobile app:
Login and tap the profile icon in the top right corner. You will then see your Referral ID under your email address.
