Instead of plain answer I'll give you a hint, trust me you get better fun from adventure
game when not trying to look for exact answers on the net.

1st digit is number you don't see in cell. You see 2 beds - so it's not "2". You see a
coat hanger with 3 pegs - so it's not "3" etc.

2nd digit - what holds inside - locked doors obviously, but how else could you escape? And
in that second way out, how many "copies" of the same obstacle do you see?

3rd digit - how many legs in cell? Including Nina's? :)

i have stuck in the first level of secret files to after i pick up the book i dont know
what to do after it