Where are external drives saved if back-up with Time machine?

Dear All,

I’m using time machine to back up my macbook on an external hard drive. Also a second external disc, where i store my photos is back-uped on that drive through time machine (in other words I have chosen to integrate the second external disc within my time machine backup). Does anybody know where I can find the second external drive that was backed up together with my machine within my time machine backups?

Any help is highly appreciated (and Im sorry if this is an already covered topic / question).