(I assume you use Exchange 2000 (e2k) or later (e2k3))
Here is a couple of ways I did it.
I hope you have a ldap client like ldp.exe or adsi edit. As an adminitrator and a troubleshooter, I love these tools. You can find public folders under CN=Microsoft Exchange System Objects,DC=<domain>.
Otherwise fire up the Active Directory Users and Computers snap-in (forever after called dsa.msc). Click on view, then click on find.
In the upper left dropdown box, select custom search. Now click on the Fields button, then select public folders then select the attribute you want to search on. I used display name.
In the textbox under value enter your criteria. In my case I used myTestFolder.
Now click on view in the upper menubar, click on choose collumns. scroll all the way to the bottom to x500 distinguished name. Add it.Your dn will be displayed next to the search results.
Would someone please tell me I missed an easy way to do this? I was annoyed at just how much trouble that was.