My husband bought a new phone today. His old one is lost. We want to back up the cloud to his phone.

If he backed up the old phone to iCloud or to his computer all you have to do is restore a backup when setting up the new phone→Restore your iOS device from a backup - Apple Support

Do you mean that you want to restore the old phone's iCloud Backup to his new phone? If so, see the iCloud section of Transfer data from your previous iOS or iPadOS device to your new iPhone, iPad, or iPod touch - Apple Support