how can i use logparser to see how many uniqe session are there by every hour in IIS Logs
According to this post it's not as easy as it seems since Log Parser doesn't support COUNT(DISTINCT), but there is a workaround in post #2.
If you're interested in useful queries there's an old post over at https://serverfault.com/questions/45516/recommended-logparser-queries-for-iis-monitoring which has some useful snippets, you could easily update the unique errors to look for a status code of 200 (although you'd have to filter out your pages only).