The easiest way to do this is by using an analytics tool to look at your old weblogs. By default IIS logs are stored in C:\windows\system32\Logfil
es.
A tool that I use to analyze logs is Smarterstats. They have a free version which allows you to analyze the traffic from a single website. It has a clean user interface that is easy to setup and use. Check it out:
http://www.smartertools.com/SmarterStats/Features/Web-Log-Analytics-Website-Statistics.aspx