How to give alert based on selected values inside form serialize

Question

I want to give an alert to what i choose on my form.

This is my dropdown on myform

<!-- PEMILIHAN TEMA -->
                <?php 
                echo "<center><div style='display:none;' id='formtugas'>";
                echo "<select id='tema' name='tema' class='form-control5' required>";
                $querytema = mysqli_query($dbh,"SELECT KodeTema, NamaTema FROM tema WHERE KodeKelas='1'");
                echo "<option selected disabled>Pilih Tema berdasarkan Tugas</option>";
                while ($ambiltema = mysqli_fetch_array($querytema))
                {
                    echo "<option value='".$ambiltema['NamaTema']."'>".$ambiltema['NamaTema']."</option>";
                }
                    echo "</select>";
                    echo "<br>";
                ?>  
                <!-- END -->

                <!-- PEMILIHAN MATA PELAJARAN -->
                <?php 
                echo "<center>";
                echo "<select id='mapel' name='mapel' class='form-control5' required>";
                $querymapel = mysqli_query($dbh,"SELECT KodeMapel, NamaMapel FROM mapel");
                echo "<option selected disabled>Pilih Mata Pelajaran berdasarkan Tugas</option>";
                while ($ambilmapel = mysqli_fetch_array($querymapel))
                {
                    echo "<option value='".$ambilmapel['NamaMapel']."'>".$ambilmapel['NamaMapel']."</option>";
                }
                    echo "</select>";
                    echo "</div><br>";
                ?>  
                <!-- END -->

This is my ajax javascript

$(document).ready(function(e) {
$("#myform").submit(function(e) {

    $.ajax({
           type: "GET",
           url: "Pengetahuan/daftarTugas.php",
           data: 
                $("#myform").serialize(), 
           success: function(data)
           {
               alert("Pilihan : " + $("#myform").serialize());
               $('#tabelTugas').html(data); 
               $('#dataTable').DataTable();                
           }
         });

    e.preventDefault(); // avoid to execute the actual submit of the form.
}); });

And this alert gives me like this Alert based on that code

I want the alert show "Pilihan : NamaTema + NamaMapel"