It's not trivial. Start by searching all of your savedsearches.conf files for the lookup file name. Then search _internal for accesses to those searches.
Then search all of your macros.conf files for the lookup file name. Find out where those macros are used then search _internal for those searches.
Finally (if I didn't forget something), search all of your dashboards for the lookup file name then search _internal for accesses to those dashboards.
--- If this reply helps you, an upvote would be appreciated.