Your post is a bit confusing.
Data transfer should have happened during setup of the new iPhone. It cannot happen after set up. If you still need to transfer data, then you need to restore the iPhone to factory and start over.
Also, not sure why you made a new iCloud account, as all your data is tied to the account it is stored in.
In short, when setting up the new iPhone, you should have logged in with your existing Apple ID / iCloud account, and loaded a backup from the old iPhone onto the new one to transfer all the data.
See here: link-> Transfer data from your previous iOS device to your new iPhone, iPad, or iPod touch - Apple Support
Once the data is transferred then you can clear the data on the old iPhone by following the steps here: link-> What to do before you sell, give away, or trade in your iPhone, iPad, or iPod touch - Apple Support