How to download WhatsApp iCloud backup?
The files are already downloaded to your Mac. The folder you're searching is on your local Mac.
As explained in the answer you've linked, the backups are stored as tar archives (tar being a program that can bundle multiple files in one archive file). You can do as they instruct:
cp *whatsapp*/Accounts/*/backup/*.tar ~/AFolderIChoose

Create the &quot;AFolderIChoose&quot; folder in your home directory before running the command. You should then see that folder populated with the backup archives. You can double them in Finder to unpack them.