Alignment of a "long cylinder"

Alignment of a "long cylinder"

Hi all,

As per the nature of my question, you can infer I am just a beginner so, thank you for taking the time to help me as, unfortunately, I couldn't find any related topic here in the community area.

How can align a part, locking all the 6 DOF, that looks exactly like a ball bar, I mean, a long thin bar with two spheres, very small in my case, one at each end?

I am having a little bit of trouble finding a way to establish a 3-2-1 due to the geometry of my part (please take a look of the picture attached, is not the real part, but resembles pretty well the situation).  My main trouble is establishing the "3" and the "1" as I have no a real plane or flat surface to take points on.

Thanks in advance for your help!