Thx for your help. I managed to get it right once after several attempts. It seems that finding the center of the bottom face is not easy for me.

If there are many ways to do it, is there an easier way?

I know that modeling should be done so that I wouldnt have to move the groups. This is a simplication of the model. At least for me it is not possible to create my model in one entity.

The image in the op is not showing the gap between the two groups

I have two groups. I want to align them like in picture. Seems to be impossible (for me anyway).
There is always space between the discs. Or they are not centered.
Have tried Move, Curic and Fredo Tools. Nothing worked.

[I use SU 2017]