pop up window

hello, i just wanted to ask for help about my code. what i wanted to happen is that when i click the button "add to cart" a pop up window will appear. here's my code:

<form action="menu.php">      
                                                            
                              <?php
                              include ("db.php");
                              
                              $data = mysql_query("SELECT price,prod_desc FROM product WHERE prod_no='1'")  or die(mysql_error());
                              while($row= mysql_fetch_array( $data )){
                                    echo"<tr><td>".$row['prod_desc'] . "</td>";
                                    echo"<td>"."<input type='number' name='qty' min='0' />"."</td>";
                                    echo"<td>".$row['price'] . "</td>"; }
                              ?>
                              <div id="cart">
                              <td><input type="submit" value="Add to cart" class="btnAddAction"/></td></tr>
                              </div>
</form>