John,

you can find it in the database by entering this query in Host :: SQL (or Settings :: SQL Console in DNN 9):

SELECT ModuleId FROM {databaseOwner}{objectQualifier}TabModules
WHERE ModuleTitle = '[MyModuleTitle]'

If this brings too much results, you can also reduce the results by adding the TabId (if you know it):

SELECT ModuleId FROM {databaseOwner}{objectQualifier}TabModules
WHERE ModuleTitle = '[MyModuleTitle]'
AND TabID = [xy]

Another way to find it is to go to module settings, right click in the IFrame (popup) and select properties. The Address looks something like
http://www.mysite.com/en-us/Home/ctl/Module/ModuleId/382?ReturnURL=/en-us/&popUp=true

Happy DNNing!
Michael