Hi nauna,
Check this example. Now please take its reference and correct your code.
HTML
<script type="text/javascript">
$(function () {
$('[id*=txtZipCode]').on('blur', function () {
var url = 'http://ziptasticapi.com/' + $(this).val().trim();
$.getJSON(url, function (response) {
$('[id*=lblCity]').html(response.city);
$('[id*=lblState]').html(response.state);
$('[id*=lblCountry]').html(response.country);
});
});
});
</script>
<table>
<tr>
<td colspan="2"><asp:TextBox runat="server" ID="txtZipCode" /></td>
</tr>
<tr>
<td>City :</td>
<td><asp:Label ID="lblCity" runat="server" /></td>
</tr>
<tr>
<td>State :</td>
<td><asp:Label ID="lblState" runat="server" /></td>
</tr>
<tr>
<td>Country :</td>
<td><asp:Label ID="lblCountry" runat="server" /></td>
</tr>
</table>
Screenshot
