Transfer your data to your new iMac
It’s easy to move your files and settings from another Mac or PC to your iMac. You can transfer information to your iMac from an old computer—or from a Time Machine backup on a USB storage device—either wirelessly, or with an Ethernet cable and adapters.
You might need to upgrade the macOS version on your older computer before you can transfer the information on it—Migration Assistant requires macOS 10.7 or later, but it’s best to update your older computer to the latest version possible. If you’re not sure which iMac you have or want to find information about other models, see the Apple Support article Identify your iMac model.
Tip: For best results, make sure your new iMac is running the latest version of macOS. Open System Preferences, then click Software Update to check for updates.
Move from a PC to a Mac. If you’re new to Mac and want to transfer from a Windows computer, see Transfer info from a PC to Mac in the macOS User Guide and the Apple Support article Move your data from a Windows PC to your Mac.
Transfer wirelessly. To transfer the data when you first set up your iMac, use Setup Assistant. To transfer data later, use Migration Assistant. Open a Finder window, go to Applications, open Utilities, then double-click Migration Assistant to do a wireless migration. Follow the onscreen instructions. Make sure both computers are connected to the same network, and keep the computers near each other throughout the migration process.
If you used Time Machine to back up your files from another Mac to a storage device (such as an external disk), you can copy the files from the device to your iMac. See Back up and restore your Mac.
Copy files from a storage device. Connect the device to any port on your 24-inch iMac or a USB-A port 
or Thunderbolt 3 (USB-C) port 
on your 21.5-inch iMac or 27-inch iMac. Then drag files from the storage device to your iMac.
Restore your content. To learn how to restore your Mac from a Time Machine or other backup, see the Apple Support article Restore your Mac from a backup.
Learn more. See Transfer info to Mac from another computer or device in the macOS User Guide and the Apple Support article Move your content to a new Mac.