Most people do not need to know the exact version (nor do they care). But in case you are troubleshooting a problem with Office, you will need to know the version.
Finding the exact version is a funny story. Why? Because the version is shown somewhere in some menu. Over time, that menu itself has been changed and moved around. Therefore, the answer to the question “Which version do I have?” is “You have to go to place x, depending upon the version you have”. 
That does not make any sense. Therefore, it is a visual answer. You have to literally look at the way Office looks (Word, Excel , etc. ) and then figure out where the version is mentioned.
Microsoft has written a detailed article with screen shots to answer this question. Here is the link Which Office version do I have?. This shows various screen shots. You open a file in Word and compare the screenshots to find the version.
Funny but true.
