Device not supported to pair

Whatever it is you hoped to accomplish by pairing an iPad and iPhone, which as razmee209 correctly suggests can't be done, perhaps this link about Continuity will help you --> Use Continuity to connect your Mac, iPhone, iPad, iPod touch, and Apple Watch - Apple Support

HausMausLV wrote:

Unable to pair iPhone and iPad. Keep getting message that it’s not supported.

That is correct you can't connect 2 apple device unless your tethering.

What exactly are you trying to accomplish.