Hi Reia_Cahill,
Thanks for posting in the Apple Support Community! We understand that the option to turn on Announce Messages with Siri is missing from your Notification settings on your iPhone.
If you haven't done so already, the first thing you'll want to do is Restart your iPhone. Once you restart, go back to Settings > Notifications and see if the option is present.
You'll also want to make sure that you're following these steps to turn on Announce Messages with Siri on AirPods.
Which generation of AirPods are you using with your iPhone and which model iPhone are you using? You can use this article to help Identify your AirPods. If you're using 1st generation AirPods, then it's expected that this feature wouldn't work with them.
If you're still not seeing this feature available, then you can also try to Reset your AirPods and then set them back up using the steps in that same article.
Take care!