frm_display_entry_content

Insert [row_num] into your view content, and it will be replaced with the row number of that entry.
Use this code to display row numbers for a table View.

add_filter('frm_display_entry_content', 'frm_get_row_num', 20, 7);
function frm_get_row_num($new_content, $entry, $shortcodes, $display, $show, $odd, $atts){
if ( $display->ID == 169 ) {
    if ( isset($_GET['frm-page-' . $display->ID]) ) {
        $page_num = absint( $_GET['frm-page-' . $display->ID] );
        $page_size = $display->frm_page_size;
        $prev_total = ($page_num - 1) * $page_size;
        $current_count = $atts['count'] + $prev_total;
        $new_content = str_replace('[row_num]', $current_count, $new_content);
    } else {
        $new_content = str_replace('[row_num]', $atts['count'], $new_content);
    }
}
  return $new_content;
}

Replace 169 with the ID of your View.