Texts from iPhone not showing up in my iPad!

You must explicitly enable Text Message Forwarding for your iPad on your iPhone.

On your iPhone:

Settings > Messages > Text Message Forwarding - set to ON - and explicitly enable your iPad from the list of devices.

Also ensure that Messages in iCloud is enabled on both your iPhone and iPad:

Settings > [Your Name / AppleID] > Messages - set to ON

More information:

How to forward SMS/MMS text messages from your iPhone to your iPad, iPod touch or Mac - Apple Support

Fault finding if needed:

If you can't send or receive messages on your iPhone, iPad, or iPod touch - Apple Support

I hope you find this to helpful in resolving the issue.

You need to make sure that you have devices that all contain the version of iOS needed in order to be able to do this. Then you need to go to your iPhone and Settings>Messages>Text Message Forwarding and you will be able to pick there what devices they get forwarded to. All the devices are going to have to be signed into the same Apple ID also in order for this to work.