How to find conformal map from half plane x<-y to circle

Question

I don't quite get the procedure of finding a conformal map.

For example the following exercise: Give a conformal map that pictures the half plane x<-y onto the disk with center 2i and radius 1.

I know that this should be a mobius map ($T= \frac{az+b}{cz+d}$) but how can I find the a,b,c and d?

Is there a general mechanism for this kind of exercises?

Thanks in advance!