I have build a model in atomistic simulation of material studio and exported the coordinates into .car format. Following this, I have modified some coordinates and save the same with a .car extension. Now, whenever I import this file into Materials Studio I am ending up with an error- 

The document could not be imported:
Failed to import document from C:\Users\gandhi\Desktop\jjj\BM_3QD.car.
- Car/Mdf File Loader Error: Car file is not in archive format 2 or 3.

Is there any other option to convert .txt format into .car format?