Since iOS 11, iOS devices have had an app called Files. It's where you can save files to your iCloud drive and view and ...
As a last resort, you can sign out of iCloud and log back in. On iPhone/iPad, go to Settings > [Your Name], scroll down, and tap Sign Out. On Mac, go to System Settings > Apple ID > Overview > Sign ...
Unboxing a new iPhone shouldn't make you anxious about whether your information will safely transfer to the new phone. These are the ways to do it easily and safely.