PARADOX it doesn't really matter if the website is in a subdomain, subfolder or other. Just look for the folder that contains all 3 of those files.
(if you previously ran the command in the wrong folder, it will have created a composer.json and vendor in the wrong location, so look for flarum and config.php as extra verification)
From your additional message, that location is very likely /home3/storiesp/public_html/forum/