How can I retrieve deleted texts

Assuming you don’t house your messages in iCloud, they are saved on your iPhone backup. Restore the backup to retrieve the messages that were present when the backup was created.

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

The answer to your question would be too long to put on a discussion page, but the following website might help: https://www.macworld.co.uk/how-to/iphone/retrieve-deleted-texts-iphone-3636380/

Hope this helps! If not, then good luck finding a solution!