If you’re getting a new phone, you’ll want to make sure that you’ve downloaded and backed up your old phone.
The iOS software does this automatically, and you’ll want to check that you’ve backed up your data regularly. To do so, head to the Settings app, then choose iCloud, and then at the bottom of the screen, choose “storage and backup”.
At the bottom of the menu, you’ll see details for the last time you backed up your data. Check the option to backup immediately if the last backup was too long ago.