To find where a particular Include page is in use, read about Incoming Links:
https://confluence.atlassian.com/conf613/view-page-information-964960667.html
To find where a particular multi-excerpt is in use:
To find all Excerpt Include macros, search by macro name. Consider opening each page in the results to determine whether the excerpt of interest is in use. Unfortunately, the functionality of finding where a particular excerpt is in use, does not seem to be available yet.