txt to off conversion is actually not text conversion, but conversion of 3D models between MilkShape 3D ASCII format and DEC 3D Object file, both formats used to store polygon graphics. We have not found any specific information about this particular conversion, beyond the fact it should be possible. Blender supposedly supports both of these files and thus is most likely your best choice, you download and use it for free, so definitely worth a try.
Updated: October 13, 2023