How to update data input on checkout page in magento2 (knockout.js)

Question

On the checkout page in Magento 2

After search data by finder code, it auto fill customers data.
But when I click the "Next" button. It will show "This is a required field."

In this post https://stackoverflow.com/questions/13632599/knockout-valueupdate-on-change-from-javascript-code

var elem = document.getElementById("input");
 elem.value = "new value";
 ko.utils.triggerEvent(elem, "change");

For example my code

jQuery('input[name="firstname"]').val("Cara");

I want to know about "ko.utils.triggerEvent" by jQuery not element