Hi ariesroses,
Thanks for coming out through Apple Support Communities for help with iMessages on your iPad. We're glad to answer this for you!
When erasing all content and settings from iPhone, you'll be prompted to enter your Apple ID password to sign out of iCloud and Apple services. Doing so may unlink your phone number from iMessages and FaceTime, so that Text Message Forwarding to other devices like your iPad is no longer supported.
This means that while you may continue using iMessages and FaceTime on iPad to connect with other users with Apple devices, iMessages and FaceTime may originate from your Apple ID, and not your phone number. Text messages send to your phone number will no longer be forwarded to Messages in iPad.
The following guide has more information:
Set up Messages on iPad
We're here for you if you've got any questions.
Have a great day!