How to make a thalamic paracellation from .mgz file

Hi. I am working on the coregistration of the electrode to the subject 2D space.

Currently, I am using ThalamicNuclei.v12.T1.FSvoxelSpace.mgz made by freesurfer. Based on this, I could make a 3D surface, but is it possible to make a parcellation using this .mgz file ?
Thank you very much for your help!