1. Jailbreak your Jailbroken/TrollStore device.

2. Install WhatsApp from AppStore

3. Install Filza from https://tigisoftware.com/cydia/ if you are jailbroken or Filza for Trollstore from https://www.tigisoftware.com/default/?p=439

4. Install AppData from https://apt.fouadraheb.com if you are jailbroken (TrollStore users, skip this step)

5. Go to your old phone which has the backup; Open Files > On My iPhone > WhatsApp

6. This is the folder that you need: "group.net.whatsapp.WhatsApp.shared"

7. Using AppData and Filza locate where is "group.net.whatsapp.WhatsApp.shared" is stored for jailbroken device or go to "/private/var/mobile/Containers/Shared/AppGroup" if you are on TrollStore

8. Delete all the data from inside that folder and paste from your backed up folder data.

9. Open WhatsApp and Login

10. Upload Chats to iCloud.

That's it!