STEP #1: Launch Settings .
STEP #2: Swipe up to scroll down the menu until you see iCloud.
STEP #3: Tap on the iCloud button.
STEP #4: Tap on iCloud Drive button.
STEP #5: Turn iCloud drive on if it is off.
STEP #6: Ensure that iCloud access for WhatsApp is turned on. Apps are list in alphabetical order, scroll down to find WhatsApp .
How to back iPhone Whatsapp data to iCloud
STEP #1: Launch WhatsApp from your Home screen.
STEP #2: Tap on Settings. It’s the gear icon in the bottom right corner.
STEP #3: Tap the Chats button.
STEP #4: Tap on Chat backup.
iPhone Whatsapp Backup: Backup WhatsApp Media on iPhone