When syncing data from iCloud, you should remember that iOS syncs large data only when on Wi-Fi and charging. Please try the following:
Sign out from iCloud, then sign back in.
Put your device charging overnight with a good Wi-Fi connection.
Be patient and keep in mind that download speed also depends on your Wi-Fi. If it's slow, downloading will take ...
it looks like you are using iTunes which is not available in the latest macOS Catalina.
Please try the same with apple configurator 2. It might help.
This error might have occurred because your macOS is not up to date.
If I remember correctly, you need to create a checksum as detailed in this Apple Help document before you can restore to another disk.
In the Disk Utility app on your Mac, choose Images > Add Checksum, then select the disk image to add the checksum to.
Click Open, then click Done.