There are different steps we have posted on this website that will help you achieve this move successfully;
See below for the different steps we will be discussing about on this post;
Method one - The email method;
Using this method all you need to do is email all your chats via and email and then download it on your iphone device follow the steps Read more here
Method Two - Using the IOS app from Play store;
Moving the messages and chat can also be very easy using the IOU app on google play store. Read more here
Method Three - Tenoshare whatsapp transfer;
Moving whatsapp is alot easier when you are using this method to transfer your whatsapp messages and chats from your android device to iphone. Read more here