How to back-up an external drive

I used my company’s computer but keep no personal data on the internal hard drive. 

I keep it on my personal data on an external WD My Book (2TB).  I also have a WD My Book (3TB) and would like to set-up an automatic backup on it.  Is it  possible to do that and how.  Thank you. 

Try this article for several suggestion that will be useful for you.