How to retrieve old text messages

If you mean you want to retrieve a text message you deleted, then you will have to restore it from a backup that includes that message:

Restore your iPhone, iPad, or iPod touch from a backup - Apple Support

Be aware that restore is an all or nothing process. You cannot restore only messages (for example) and any information on your device between now and when the backup was made will be lost.

Asked and answered in this thread that you posted: Retrieve text messages

Cheers,

GB