@Meenakshi,
We have indeed hit a roadblock and need to take a diversion. I couldn't find a way to reach the destination external drive in DOS run TestDisk.
However, I have now confirmed that you can copy a selected file/folder to the pendrive itself.TestDisk itself occupies only 28MB space in the pendrive. So practically you can easily accommodate 6GB data on your present 8GB pendrive. See your screenshot in post #38. You are in Directory C:/. Give the copy command c. Your selected folder/file will be copied to the pendrive.
So now there are two solutions.
1. Select only one folder/file not exceeding 6GB and copy it to the pendrive. Move it to your external HDD and copy another folder.
2. Buy a large enough pendrive like say 128GB, run TestDisk from it to straightaway copy large chunks of data.
If you need some important data immediately go by the above process. I have no other solution to offer at the moment.