Increasing concurrent requests in DropNet

Question

I have some giant folders saved in DropBox with more than 10k files in them. I want to check if a list of files exists there, but I can't get the metadata on the parent folder because I am over the 10k limit.

So I have written code to check if each file in a list of files is present.

What I can't figure out is how many requests will run concurrently and how can I increase this number to the max that my machine can handle?

foreach(string f in files)
            {


                client.GetMetaDataAsync("/blah/blah/" + f, (response) =>
                {
                    found.Add(f);
                    count++;
                    Console.WriteLine("{0} of {1} found - {2}", count, files.Count, f);
                },
                (error) =>
                {
                    if (error.Message.Contains("[NotFound]"))
                    {
                        missing.Add(f);
                        count++;
                        Console.WriteLine("{0} of {1} missing - {2}", count, files.Count, f);
                    }
                    else
                    {
                        Console.WriteLine("Unknown error");
                    }
                });
            }