Check your TSA PreCheck approval email or letter for your Known Traveler Number (KTN)
Log in to your Trusted Traveler Program (TTP) account at https://ttp.cbp.dhs.gov/
Open your profile/known traveler information to view your KTN
Find your KTN on your membership card (if you received one)
Review your airline reservations to see if your KTN was saved with your frequent flyer profile
If you can’t find it, contact TSA or the Trusted Traveler Program support listed on the TTP website