Picking a node within a 3D Solid Volume

hi all,

I have a solid 3D part made of concrete. I would need
the results of a few points inside the concrete. However, I realised it
was not easy to pick them when doing a Set because the nodes are hidden
(they are not on the surface. I have 1) partition my model exactly at
the points when I need to pick 2) i name the points as datum points.

Using the CAE interface, how can i pick this nodes? I have attached a pic for better understanding. Can anyone please advise?

Thank you.