3 Ways to Retrieve Deleted WhatsApp Message on iPhone 
How to Recover Deleted WhatsApp Messages on Android? 
How to Restore Deleted WhatsApp without Backup [2022 Update]
[2 Ways] How to Recover Deleted WhatsApp Messages?
It might take some time, if you have lots of contents.
You need just 1 click to transfer not only chats but attachments.
Except the local backup, the most common choice may be the Google Drive, a safe tool to backup and access all our files, including the WhatsApp data, from any devices.
One drawback of this option is that the existing iPhone files would be replaced with the backup after the restoration.