Locating Site Number ...

This appears to be an awesome plugin, I have yet to get it to run properly on my site ... I am running wordpress multisite ... I have membership premium plug in that should control the entire site... I have to tell it which site is the master site so I made a site called registration that will handle everything... so how do I find the number it is assigned so I can place it in the Global Table as the master site ?... like the very first site number is 1 (I can't use that site for a number of reasons all security related)... so I counted down the list and it was say number 5 in the list but when I used that number it didn't do anything ... so How do I find what number a wp multisite is ?