Forgot my Gmail password

iCloud uses Apple ID credentials.

If you do not remember the Apple ID Password then follow the steps given in this Apple Article -> If you forgot your Apple ID password - Apple Support

If you do not remember the Apple ID then follow the steps given in this Apple Article -> If you forgot your Apple ID - Apple Support

Change your password · On your iPhone or iPad, open the Gmail app . At the top right, tap your profile picture or initial · At the top, tap Personal info. 

Change or reset your password - iPhone & iPad - Gmail Help