How do I retrieve messages I accidentally deleted

See How to retrieve deleted text messages on iPhone

https://www.macworld.co.uk/how-to/iphone/retrieve-deleted-texts-iphone-3636380/ and

How to Recover Deleted Text Messages on Mac https://www.ibeesoft.com/recover-mac/recover-deleted-messages-imessages-mac.html

Also, note that deleted messages are saved in iPhone backups. To recover them from a particular backup, use Restore your iPhone, iPad, or iPod touch from a backup - Apple Support

If you were syncing Messages with iCloud and deleted them, they can't be recovered.