Where is MMS on IPad? (Not IPhone---found it there)

There is no MMS setting on an iPad. An iPad cannot send SMS nor MMS texts natively. If you couple it to your iPhone with iOS Continuity then you can send from the iPad via the iPhone (see Use Continuity to connect your iPhone, iPad, iPod touch, and Mac - Apple Support ). Only a cellular telephone can natively send SMS/MMS text messages.

On your iPhone go Settings > Messages > Text Message Fowarding > (iPad) > Toggle On

Make sure the iPhone is set up to share messages with the iPad and you've accepted that request on the iPad as indicated in the continuity instructions I posted. Also on the iPhone, make sure send as SMS is enabled.

iMessages from Apple to Apple devices will always work as those are handled by Apple and any and every iOS device can natively handle them. However, to send or receive SMS/MMS texts, you have to use continuity to pair your iPad with your iPhone - only your iPhone can actually send or receive an SMS/MMS message as those are handled by your cell phone carrier and their equipment using your phone's voice channel connection. Your iPhone can then share those with your iPad via continuity.

Michael Black wrote:

Also on the iPhone, make sure send as SMS is enabled.

For what it's worth, all "Send as SMS" does is tell the phone to sent an iMessage as an SMS if it fails as an iMessage. It doesn't turn SMS on or off. Only the carrier can do that. It doesn't have any affect on text forwarding that I've been able to find.