Q: cannot send text to non apple device from my ipad

On your iPhone, go to Settings> Messages>Text Message Forwarding and make sure your iPad is enabled.

The settings Meg mentioned are not on the iPad, they are on your iPhone.  You need to make sure the iPhone has enabled continuity with the iPad to send SMS texts from your iPad.  An iPad cannot natively send SMS texts - it can only do that if it is properly paired with an iPhone using iOS's continuity features.

See Use Continuity to connect your iPhone, iPad, iPod touch, and Mac - Apple Support

As explained in the link I posted:

Set up SMS and MMS with Continuity

1. You need iOS 8 or later on your iOS devices and OS X Yosemite or later on your Mac.
2. Sign in to iMessage with the same Apple ID on your iPhone, your other iOS devices, and your Mac.
3. On your iPhone, go to Settings > Messages > Send & Receive. Add a check to both your phone number and email address. Then go to Settings > Messages > Text Message Forwarding and enable the device or devices that you want to forward messages to.
4. Look for a code on the Mac, iPad, or iPod touch that you enabled. Then enter this verification code on your iPhone.