Main Search Omeka S

I’m trying to find the code from the main search ( not the advanced ) to change it a little bit -> input type=“hidden” name=“record_types[]” value=“Item” id=“record_types” , but i was looking in the php files , and i can’t find it , maybe it’s a js? or something like that , do anyone have found it?
i red something about a [ hoffman-test.html ] file , but it is not in the omeka files or i haven´t found it , maybe it has another nickname or some stuff like that

Is your question about Omeka S or Classic? You posted it under S but I sounds kind of like Classic to me.