Voice Memo which are always in M4A format lets you record and store short voice messages that you can play back at any time. Many phones with this feature also let you record parts of phone conversations in progress.
If you delete them by accident, you can use iPhone Data Recovery to store them again. Not only Voice Memo, but also Contacts, Messages, Call history, Calendar, Notes, Reminder, Safari bookmark, WhatsApp are also supported to be recovered.
Connect your iPhone 3GS to computer via USB cable and click "Start Scan" button on the interface. You need to download a plugin and follow the three steps below to enter the scanning mode.
1. Hold your iPhone and click "Start".
2. Press and hold the Power and Home buttons at the same time for exact 10 seconds.
3. Release Power button and keep holding the Home Button.
Select Vioce Memos on the left sidebar and all the recoverable vioce memos will be displayed on the right side. You can switch on the "Only display the deleted item(s)" toggle at the top of the interface.