Fdem,
you just upload what you have. I posted my original track here (above). That's the file I uploaded in Suno. For the country version I uploaded the edgy duplicate that Suno created. The country version is a cover of the edgy cover. The files I uploaded in Suno consisted of the vocals and the complete arrangement. You don't have to extract anything. It's easy. Upload what you've got and go to "create" and "cover song". That's it.