If your Apple ID has 2-Factor Authentication enabled, we will definitely need to schedule a brief 5-10 minute phone call during which time you can authorize this new Mac to properly sync with your Apple ID using your mobile phone as an authentication device.
Please keep in mind that newer (2018 and newer) Macs do NOT have USB-A ports (the rectangular USB ports that you may have gotten used to on your older Mac). Newer Macs have only USB-C Ports, so if you have any USB-A compatible devices that you would like to plug into your new Mac, it will require a USB-C to USB-A Adapter (typically $9.95).