I recently copied a large set of files (about 6 GB) into my Pen Drive. Is there any way to determine the time taken to complete copying from any of log files. I am using Mac OS Mountain Lion Operating System.
Not from a log file, no. You can, however, use the terminal's
This will start a timer, copy the entire folder you list over to your pen drive and output how long the whole process took.
Here is a real world example using a folder on my desktop named "partslist" and an external USB drive named "Drive Two":
And from the output in Terminal I can see it took just over half a second (you want the value for "real"):