“Show recently deleted” option does not come up under edit. Can someone please help?

When you read the info in the Apple Support document linked above your name carefully, note that......

iOS 16 must be installed on your iPhone

You must have deleted the message(s).....after....you installed iOS 16 on the phone

No more than 30-35 days have passed since you deleted the message

Bottom line.......

Show Recently Deleted will not appear if no messages have been deleted since you installed iOS 16.

If you are trying to retrieve a message deleted before you installed iOS 16, the message is gone.

If you read the support document before you posted your question, you will remember that the first requirement is that iOS 16 must be installed on your phone to be able to retrieve messages.

Unfortunately, your phone is too old to be qualified for the iOS 16 update. The message is gone.