Form entries are not stored in views. Views display content that is stored in Formidable's frm_items and frm_item_metas tables. Before you can search for a value in a view, the view has to be rendered on a page where you can search with the browser, but not WordPress search. You could create your own search form using Formidable. See this: https://formidableforms.com/knowledgebase/create-custom-search-form/