Well, technically that’s an error 🙂
The page / URL should be something like this;
https://DOMAINNAME.EXTENSION/wp-admin/tools.php?page=acf-cleaner%2Facf-cleaner-admin.php
And the page requested should be on your server (check it by (s)FTP) like this;
/public_html/wp-content/plugins/acf-cleaner/acf-cleaner.php
Of course the last part (/wp-content/…) is the most important for now.