Depending on which device you are using, there may be an option for you to transfer your chats.
Learn more about transferring your chats on: Android | iPhone | Windows Phone | Nokia S60 | BlackBerry 10
Nokia S40 and BlackBerry devices cannot transfer chat history at this time.
If you are trying to recover your deleted chats, learn how to on: Android | iPhone | Windows Phone | BlackBerry | Nokia S60 | BlackBerry 10
WhatsApp Support Team