If you applied for the IPO through Kite using the PhonePe UPI app, PhonePe will send you a notification for the mandate.
If you missed the notification, log in to the PhonePe app and tap on the bell icon to see the notification.
Tap on Accept and validate your application by entering your UPI PIN. Then, verify your IPO application number by checking your registered email ID. Your application number will include your 6-digit Zerodha user ID.