How can I access the JSON data, if I already have it saved in a variable?

This is the JSONone I have:

Optional({
    Cuenta = 1;
    Datos =     (
                {
            "usr_apemat" = "";
            "usr_apepat" = damas;
            "usr_celular" = 0;
            "usr_codigopostal" = 123457;
            "usr_direccion" = Campeche;
            "usr_email" = "[email protected]";
            "usr_fechanac" = "0000-00-00 00:00:00";
            "usr_fotolink" = "";
            "usr_id" = 7;
            "usr_idestado" = 0;
            "usr_idpais" = 0;
            "usr_idsangre" = 0;
            "usr_idsexo" = 0;
            "usr_nombre" = pedro;
            "usr_password" = damas;
            "usr_rfc" = "";
            "usr_swbaja" = 0;
            "usr_telefono" = 1278932;
            "usr_username" = damas;
        }
    );
    Error = 0;
    Mensaje = "Se Realizo la consulta con exito";
    Pasaporte =     {
    };
    nPasaporte = 0;
})

and this is my code:

let usr_username = usernameTxt.text!.lowercased()
 let usr_password = passwordTxt.text!

            let parameters = ["Accion": 2, "Datos":[ "usr_username": usr_username, "usr_password": usr_password]] as [String : Any]

            // send request to mysql db
            // url to access our php file
            let url = URL(string: "http://sipot.conanp.gob.mx/server/pasaportes.php")!
            let session = URLSession.shared
            // request url
            var request = URLRequest(url: url)

            // method to pass data POST - cause it is secured
            request.httpMethod = "POST"

            do {
                request.httpBody = try JSONSerialization.data(withJSONObject: parameters, options: .prettyPrinted)

            } catch  {
                print(error.localizedDescription)
            }

            request.addValue("application/json", forHTTPHeaderField: "Content-Type")
            request.addValue("application/json", forHTTPHeaderField: "Accept")

          let task = session.dataTask(with: request as URLRequest, completionHandler: { data, response, error in

             guard error == nil else {

                   return
             }

            guard let data = data else {
                    return
                // no error
                if error == nil {

                    do {

                        let json = try JSONSerialization.jsonObject(with: data, options: .mutableContainers) as? [String: Any]
                        guard let parseJSON = json else {
                            print("Error while parsing")
                            return
                        }

                        // si mando a imprimir id el json me devuelve solo los datos pero de alli ya no puedo entrar a los datos generales del usuario

                        let id = parseJSON["Datos"]
                       // let datoJson = id["usr_nombre"] as! [AnyObject]?
                       // print("hola 3",id)
                        //let datoJson = id?["usr_nombre"] as? String
                   //     let arrayJSON = id?["usr_nombre"] as? String
                    //  print("print 1",datoJson)
                        // successfully logged in

                        if id != nil {
                           print("hola 3",datoJson)

                            // save user information we received from our host

                            UserDefaults.standard.set(parseJSON, forKey: "parseJSON")
                            user = UserDefaults.standard.value(forKey: "parseJSON") as? NSDictionary
                             print("hola 1", user)
                            // go to tabbar / home page

                            DispatchQueue.main.async(execute: { 
                                appDelegate.login()
                            })

                        // error
                       } else {

                            // get main queue to communicate back to user
                            DispatchQueue.main.async(execute: {
                                let message = parseJSON["Mensaje"] as! String
                                appDelegate.infoView(message: message, color: colorSmoothRed)
                            })
                            return

                        }

                    } catch {

                        // get main queue to communicate back to user
                        DispatchQueue.main.async(execute: {
                            let message = "\(error)"
                            appDelegate.infoView(message: message, color: colorSmoothRed)
                        })
                        return
                    }

                } else {

                    // get main queue to communicate back to user
                    DispatchQueue.main.async(execute: {
                        let message = error!.localizedDescription
                        appDelegate.infoView(message: message, color: colorSmoothRed)
                    })
                    return

                }

                })
           task.resume()
        }

    }