Presumably you are connecting your wired headphones to your iPhone with a Lightning to 3.5mm Headphone Jack Adapter - whereas your iPad10, with a USB-C port, will instead require a USB-C to 3-5mm Headphone Jack Adapter.
Given that your iPhone+Adapter works with your wired headphones, this would suggest that the problem may be with the Adapter that you are using with your iPad.
Faultfinding is most easily conducted through testing with another device (in this case, another USB-C equipped iPad) or substitution of the Adapter.
If you need assistance, you might be best advised to visit the Genius Bar at your local Apple Store or Apple Authorised Service Provider (AASP) - where the technicians will be able to test and assess your iPad, Adapter and headphones:
Genius Bar Reservation and Apple Support Options - Apple