No PIN required at checkout
You should not be asked to enter a PIN number on a PIN pad. If you are, tell the cashier that you are using a commercial card to checkout.
If your program utilizes program-specific purchase cards, make sure the cashier knows you are purchasing with your commercial card and then swipe or provide your purchase card at checkout like you would with a normal credit card.
Be sure to provide any additional purchase details, like if you are tax-exempt before checkout begins.
If you do not have your card at checkout, the cashier will manually look up your account by email. You will be sent a 2FA verification code that you will provide to the cashier at checkout. This 6-digit code will be sent via email or text message, depending on the verification method you set up when creating your account.