The FEM 3D mesh are dedicated only to FEM forward modeling, this has nothing to do with defining parcellations of the cortex surface.
https://neuroimage.usc.edu/brainstorm/Tutorials/Duneuro
If you want to use the Schaefer parcellation, either on the surface or in volumes, process the T1 MRI of the subject with CAT12:
https://neuroimage.usc.edu/brainstorm/Tutorials/SegCAT12