how do I get "read" notifications on text messages ive sent on my iphone 7 plus

Read notifications are only seen on iMessages for those that have enabled "read" receipts. You can enable the feature for all contacts by going to Settings | Messages | Send Read Receipts. If you want to enable it for a particular contact, open messages, find the person you want to send read receipts to, click the "i" in the upper right and turn on Send Read Receipts.

There isn't a way to get or send read receipts for those using SMS messaging.