[Freesurfer] Convert label file to STL file‏

Dear Freesurfer Experts,

I'm trying to convert .label file to .stl file. In more detail of my purpose, I want to get separate stl files of whole brain. Now, I want to make stl files of label files which made from ?h.aparc.a2009s.annot.

First, I tried to convert lh.pial to lh.pial.stl, I've got it (this was just check how mris_convert works). Second, I copied lh. white file from surf dir into label dir. Then, I runed next command:

cd <subjid>/label mris_convert --label lh.bankssts.label bankssts lh.white lh.bankssts.label.stl

And got the error message: ERROR: unknown file annot file type specified for output: lh.bankssts.label.stl

Do you know what could have gone wrong?

Thank you, Yuki.