If you have Luminate Online, you will have two site IDs.

When registering for bbcon, you will need your Blackbaud site ID.  You can find this ID on Blackbaud.com.  See this article (BB118989) for details on how to view it.
 

For the Luminate Online site ID, you can find this ID by viewing transaction confirmation codes. See this article (BB740226) on understanding confirmation codes.