Extract OAR contour matrix from contoured 3D CT-scan images

Dear community,

I am new to 3D Slicer, and I have a complete RT plan (CT (a set of image slices), RTPLAN, RTDOSE, RTSTRUCT) and I wanted to extract OAR contour matrix from the contoured 3D CT-scan images. Can I extract it using 3D Slicer, and if so, what steps I need to follow to extract that matrix for each OAR?

Thank you so much!!

Best regards,