how to view deleted messages

The pre-iOS 16 method of retrieving deleted messages was totally different. I believe it no longer works. But I’ll say what it was here, just in case it still functions (which I doubt).

Unless you house your messages in iCloud, they are saved on your iPhone backup. Restore that backup to retrieve the messages that were present when the backup was created.

Writing an effective Apple Support Commun… - Apple Community

Update your Apple devices if they are recent enough to support the updates!

Read and follow the article linked above … assuming you’re using iOS 16 or greater.