How to Transfer WhatsApp Chat History from iPhone to Android
How to backup or transfer WhatsApp chat data on your new phone
How to Transfer WhatsApp Messages from Android to iPhone (Through Email Export)
WhatsApp tips: How to transfer old WhatsApp chats to a new phone
How to Transfer WhatsApp to New Phone 
Download your GBWhatsApp package and install it into your phone.
Click Start Transfer button to start transferring WhatsApp chats between two devices.
You will see a screen as below.