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Some of the iCloud data will sync when you enable iCloud, but not all. If you want to copy the entirety of the iCloud info, you would need to restore from iCloud backup vs. setting it up as new. To get to that, you'd have to go to Settings -> General, then scroll down to Reset and choose Erase all content and settings. When the phone comes back, it will ask you to restore from iCloud.
Warning - if you didn't back up to iCloud, and just had iCloud enabled, this won't do you any good, so only do this if you know you have an iCloud backup.