Need Help Using the Replace Tool

I switched hosts and upgraded to 2.3.  All is well except for my pictures.  You can see the result here:

http://www.moscertificationtraining.com/learn

All of my picture and PDF links are broken and have read that using the Replace tool at admin/tool/replace/index.php is the way to go.  When I get there, I am not sure what to physically put into the boxes.

Do the "previous server URL" and "new server URL" refer to the path on the CFG Root line of the Config file?  If so, how do I obtain the old server's root path if I no longer have it?

David