You would be better off replacing the massive switch() statement with
something like the following:
digitalWrite(mn1, mnc & 1);
digitalWrite(mn2, (mnc >> 1) & 1);
digitalWrite(mn3, (mnc >> 2) & 1);
digitalWrite(mn4, (mnc >> 3) & 1);
digitalWrite(mn5, (mnc >> 4) & 1);
digitalWrite(mn6, (mnc >> 5) & 1);
If you don't understand why that works, let that be an exercise to go
figure out why it works! 
and why it uses much less memory!