My old hardrive have errors so my new host put a new one and the other as slave...

I want to copy my old virtual servers (i didnt backup with virtualmin module), so thats why I want to know in what file are stored so I just simply copy that file(s).

you might want to have a look at /etc/webmin/virtual-server/domains
I'd prefer to make a backup first of the domains through the virtualmins backup tools and restore them onto the new disk