Generate Static Page to Show Search Results/Detail for API

I’m not so professional in this but I have a solution you can try. You can create custom page templates in WordPress and place your form code in that template and in another template create your result page and pass the query using POST method to the result page template. Then with php you can get the search query using $_POST and get information from your API. I’ve done this same thing with one of my plugins.

In your search form template:

<form action="yoursiteurl.com/resultpagename" method="post">
  <input type="text" name="search" />
</form>

In your result template:

$search_query = $_POST["search"];

$response = wp_remote_get('https://ecourier.com.bd/apiv2/?product_id=' . $search_query);
$body = wp_remote_retrieve_body( $response );
$data = json_decode( $body, true );

var_dump($data);

Let me know if this works or not.