How can I export 2 overlayed volumes to dicom files or save 2 overlayed volumes to a single nifty file?

Support
1

Operating system:Windows
Slicer version: 4.11.20200930
Expected behavior: Save two overlayed modules into a single nifty file or dicom files
Actual behavior:

2

This topic should help: How to stitch together two sets of CT slices to make one file