yes you need enter hdfc net banking or input debit card details to reveal the hdfc upi bin no 16 digit and exp date and cvv no.
Then login your hdfc account in hdfc net banking in click to cards section and click credit card and then register a new credit card
enter rupay card details and your upi card will be added.
then open hdfc banking mobile app then card section select upi card and set card the pin.
go to paytm or gpay add upi card enter last six digit with exp date.
first they ask for card pin enter the card pin as you set in hdfc mobile pay and ask for set a new upi pin l, enter the pin then your upi pin is successfully registered.
now you scan merchant code in store and pay in hdfc rupay upi credit card.