Call WWW Outside the Main Topic

I am using the Parse SDK for Unity to retrieve some files and save to the resource directory. When I call parse.findAsync (), it creates another task, and it is impossible for me to call WWW to load the URL obtained from the analysis. I need:

• Parse Challenge
• Get information about the parade
• Call www for every file i got from the session
• Wait for it to be completed;
• Return result;

I tried this:

      public IEnumerator GetXXXAsync(String objectId){
        var query = ParseObject.GetQuery("xxx").WhereEqualTo("yyy", ParseObject.
        CreateWithoutData("zzz", objectId));

        List<String> urlList = new List<String>();
        Album album = null;

        query.FindAsync().ContinueWith(t =>
                                       {
            var tasks = new List<Task>();
            Task task = Task.FromResult(0);
            foreach (var result in t.Result)
            {
                ParseObject obj  = result;      

                ParseFile file = (ParseFile)obj.Get<ParseFile>("image");
                if(file != null){
                    urlList.Add(file.Url.ToString());
                    tasks.Add(GetImageAsync(file.Url.ToString(), "image.png")); 
                }               


            }

            // finished.
            return Task.WhenAll(tasks);
        }).Unwrap().ContinueWith(_ =>
         {
            gameManager.SendOk();

        });

        return null;
      }

      private WWW WaitForImage(String url, string filename) {   

        WWW www = new WWW( url );
        while(!www.isDone){
            Debug.Log("Waiting");
        }
        Utils.SaveFileFromTexture(www.texture, (gameManager.GetResourcesPath() + "/Textures/" + filename));
        Debug.Log("Saving file ");
        return www;     


    }


    public Task<WWW> GetImageAsync(String url, string filename) {
        var task = new TaskCompletionSource<WWW>();
        Debug.Log("GetImageAsync " + filename);
        task.SetResult(WaitForImage(url, filename));
        return task.Task;
    }

I tried to get IEnumerator instead of WWW, but I always get that WWW "cannot be called outside the main thread". Is there anything I can do to call WWW outside the main thread? Or something else?

Tks