Aligning/rotating vectors

Say I have two points, A and B. I can subtract A from B to find the vector pointing from A to B. Now, I’d like to rotate a model to be aligned with this vector. In my case, the model is a human character model, and I’d like to have it’s shoulder be aligned with the vector we found. How would this be done? I’ve been trying LookRotation and FromToRotation, but I never seem to get the model aligned with the vector.

The larger problem I’m working on is that I have the raw positions (x,y,z) of the joints of a human (i.e. if i connect all the points, I get a stick figure). I want to rotate the corresponding joints of my model so that the model mimics the stick figure.

Any help or suggestions are very much appreciated!

In case it helps anyone: my main oversight was that LookRotation() points the +z direction in the direction of the given vector. I was able to accomplish what I was trying to do using the answer from this thread: unity - LookRotation() make X axis face the target instead of Z - Game Development Stack Exchange