Well, I had this problem before. I want to change my old iPhone SE to iPhone 7 because my old iPhone is not working well. But as I reflect, I was thinking if I can transfer all my data to my new phone since every bit of data on my old phone (especially on WhatsApp) are very important to me. So, I researched and found the solution to my problem. I've read this article https://echoshare.co/transfer-whatsapp-history-old-iphone-to-new-iphone/ and tried the solution they offer, and it worked like magic!!!! gosh. Sharing this to you, this might help you :)