there are many ways to identify  and then break  the links.

In your case, where you have a large workbook, and many links, I
would suggest the following:

Andrew's Utilities (Available at
http://www.andrewsexceltips.com/my_utilities.htm)

Choose the type of installation you prefer, and then under the
menu "Other", you will find an option to break external links.

It is a great productivity enhancer, and I'll gladly advertise it
for free!!!