Deleted messages from other iPhones

Hello A_DiSabatino,

Thanks for using the Apple Support Communities!

If you have messages on an older device that you want to sync with your current device, you may want to look in to setting up Messages in iCloud. This article can provide you with some info about that and how to set it up: Set up iCloud for Messages on all your devices - Apple Support

Alternatively, if you have a backup from your older device, you can use these steps to restore that to another iPhone: Restore your iPhone, iPad, or iPod touch from a backup - Apple Support

Please note that if you restore a backup, anything that's changed since the backup was taken will no longer be available.

Hope this info helps!

Select all existing read messages and mark them each as unread.

An Apple wouldn't dare delete an unread message under threat of perjury, and if it did, at least you tried and can request this functionality at the top of yur lungs.