Disk Brakes on Nishiki Pueblo I have a Nishiki Pueblo and I am looking to put disk brakes on it. 

My problem is that I am not sure which disk brakes fit on my bike. 

Thanks in advance.
for what I see online about your bike, you don't have fitting for disc brakes.
You could upgrade to better V brakes, or Cantilever brakes, even idraulic Magura rim brakes, if power is what you are looking for, but disc brakes won't fit on your frame.