How to transfer everything thing to your iCloud?

Can you elaborate on "Everything".

When you turn on iCloud, information that are synced and stored in iCloud, are Contacts, Calendars, Bookmarks, Mail, Notes, Voice Memos, shared photos, iCloud Photos*, Health data, call history, and files you store in iCloud Drive.

*-If you had turned on iCloud Photos, your content is automatically stored in iCloud. 

This should help.

About storage on your device and in iCloud - Apple Support