To pass a query string to a request node, you need to add the query to the URL. So the input msg needs to have a msg.url (which you could build dynamically by using JSONata in a change node) or you can specify the URL in the node and use mustache style variables:
Note that msg. is not supplied in the mustache variables. Also note that using double brackets {{...}} would man that mustache would escape any characters that would be mis-interpreted as HTML which is why triple-brackets are needed.