Hi griffyg55,
The support article you need is Forward SMS/MMS text messages from your iPhone to your Mac or iPad:
"Automatically forward texts to your other devices
- Make sure that you're signed in to iMessage with the same Apple ID on each device:
- iPhone or iPad: Check the Apple ID shown in Settings > Messages > Send & Receive.
- Mac: Open the Messages app, choose Messages > Settings (or Preferences), then click iMessage. Check the Apple ID shown.
- On your iPhone, go to Settings > Messages > Text Message Forwarding.
- If you don't see Text Message Forwarding, go to Settings > Messages. Turn off iMessage, then turn it back on. Tap Send & Receive, tap Use Your Apple ID for iMessage, then sign in with the same Apple ID used on your other devices.
- Choose which devices can send and receive text messages from your iPhone:
- If you choose a device that isn't using two-factor authentication for your Apple ID, a verification code appears on each of your other devices: enter that code on your iPhone.
As long as your iPhone is turned on and connected to Wi-Fi or a cellular network, new SMS/MMS texts can be sent and received on the devices that you added."
Follow those steps to get your messages on both the iPad and iPhone.
Regards.