Now that I can read the probability expression, I can provide some help. To find the probability of finding a 1s electron in a sphere of radius a0, you're going to need to integrate that probability expression from r = 0 to r = a0.
When you make the substitution x = r/a0, dx = dr/a0. I don't see dx in your integrand (or even an integral at all). You showed the results of integration by parts, but not the work, so unless I duplicate your work, I can't say that your work is correct.