Hello Anjali,
The annot files are created when FreeSurfer parcellates the surfaces. You seem to want to map the volumetric atlas labels onto the surface models for the N27 brain. You could do something like that with 3dVol2Surf using the N27 brains that are in the same space as the atlas (http://afni.nimh.nih.gov/pub/dist/tgz/suma_TT_N27.tgz,
MNI N27).
cheers,
Ziad