How do I download photos and videos from iCloud backup?

To restore from a backup, see Restore your iPhone, iPad, or iPod touch from a backup - Apple Support

youll first erase the entire contents of your device.

if you mean iCloud sync, anything in iCloud is also on your device. Adding or deleting on one device reflects everywhere. Sync is not a backup.

If you're using iCloud Syncing for your photos, they are not part of the backup.

This is the Apple community, not the apple chat-with-us platform.

And your data is Encrypt so apple can’t read it.