HttpWebRequest from basic to modern authentication

Question

I have a script dat i want to convert to modern authentication. I cant find the right properties to do it. Could you help me?

HttpRequestCachePolicy policy = new HttpRequestCachePolicy(HttpRequestCacheLevel.Default);
HttpWebRequest.DefaultCachePolicy = policy;
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(destinationUrl);
HttpRequestCachePolicy noCachePolicy = new HttpRequestCachePolicy(HttpRequestCacheLevel.NoCacheNoStore);

request.CachePolicy = noCachePolicy;
request.Method = "GET";
string encoded = "username:password";

request.Headers.Add("Authorization", "Basic " + encoded);
request.ContentType = "application/xml";
request.Headers["x-api-key"] = "12312312-1234-1234-1234-123123123123";

ServicePointManager.ServerCertificateValidationCallback = delegate (
Object obj, X509Certificate certificate, X509Chain chain,
SslPolicyErrors errors)
{
     return (true);
};

HttpWebResponse response;
            try
            {
                response = (HttpWebResponse)request.GetResponse();

                if (response.StatusCode == HttpStatusCode.OK)
                {
                    Stream responseStream = response.GetResponseStream();
                    string responseStr = new StreamReader(responseStream).ReadToEnd();
                    Console.WriteLine(responseStr);

                    return responseStr;
                }
            }
            catch (Exception e)
            {
                 
                Task.Run(() =>
                {
                    
                });
            }

I probaly need something like ConfidentialClientApplicationBuilder but i cant seem to find how to do it.