The easiest way to retrieve the desired username and password in iCloud Keychain is by launching Safari and locating Preferences > Passwords. It’s here where the hunt for the username and password begins, but fortunately macOS has two ways to access this info.
Still, there are times when you might need to know the saved account username and password that are stored in iCloud Keychain, for example when an online service you have signed up to also has a Mac app that requires those same login credentials. Saving and retrieving a password is easy, but it's only effective if you have enabled AutoFill in Safari preferences. Get a 50% Discount How Do I Access My Passwords in iCloud Keychain on a Mac?