In academic music theory parlance, you'll be forced to memorize that this chord is always built with the 3rd of the chord in the bass . . . which means first inversion, which means the figured bass symbol is "6".
But what you should know - whatever key you're in, the chord is the MAJOR triad built on the pitch a half step above tonic. Example - in the key of C minor, it is Db Major. Example - in the key of C Major (not minor this time), it is STILL Db Major. Easy, no?
Another example . . . A minor? Bb Major. And you're gonna love this one ---> E minor: F major. Delicious.
