How to join two sets of CT slices and change the volume?

Hi, I’m new to 3D slicer, I’m trying to join two bone CT scans into a single file, but I can’t see the slices in R, Y and G views. I would like to change the volume so that all slices appear. I hope I was clear, I don’t speak English well. I send some images.

Thank you in advance for your attention and help.