Hiding attachment/system fields on ticket form

I am not a programmer, so I'd like to ask for some help in the community. I tried using the code snip that Kristin posted 3 years ago, but it is not working for me. I copied it below and adapted to one form only:

//Form Submit
$(document).submit(function() {
//set a string to equal the custom field value
var subjectstring1 = $("#request_custom_fields_360026456434").val();
//set subject to equal a string including field value string
$('#request_subject').val("Request Received From " + subjectstring1);
});
//End Form Submit

In the past few years, has the format changed? Can you see anything wrong with this code?

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