3D Slicer reconstructs 3D volumes from the input 2D image slices and no reference is kept to 2D slice indexes. However, you may find that one of the voxel indexes that slicer displays in the Data Probe section in the lower-left corner correlate with DICOM slice index (most likely there will be an offset of 1, since DICOM usually start the numbering at 1 instead of 0).
