Is there anyway to format my EndPoint URL in WordPress?

You don’t. Query args are not part of the route URL. Your endpoint URL is:

https://iotkidsiq.com/wp-json/zaindob/v1/sync_order

So needs to be registered as:

register_rest_route( 'zaindob/v1', '/sync_order', array( 
    'methods' => 'GET',
    'callback' => 'updatetable',
) );

key and msisdn are arguments that are sent to your endpoint. To define these use set the args property of the endpoint options:

register_rest_route( 'zaindob/v1', '/sync_order', array( 
    'methods'  => 'GET',
    'callback' => 'updatetable',
    'args'     => array(
        'key'    => array(
            'type'     => 'integer',
            'required' => true,
        ),
        'msisdn' => array(
            'type'     => 'integer',
            'required' => true,
        ),
    ),
) );

Now your endpoint callback can accept the key and msisdn paramaters, and they are required for the endpoint to return a result:

function updatetable( $request ) {
    $key    = $request->get_param( 'key' );
    $msisdn = $request->get_param( 'msisdn' );

    // etc.
}