@kuangmichael07, if you imply search within your own web application search page then you need to utilize trackSiteSearch method of the tracker. This will allow you to capture the page number.
The fields mkt_* and populated by means of Campaign attribution enrichment and depends on the mapping you configure the enrichment with linking “mkt” fields to the querysting key/value pair.
The refr_* are populated by values resulted from the parsing “Referer” header by means of Referer parser enrichment.
Those 2 are described and explained in Web traffic driven campaign tracking with Snowplow [tutorial]. None of them is meant to capture the page of the search result for you. You need to do some workaround if you know where the page number is expected to be (presumably somewhere within querystring?).