You could use RTVQMQRY against each of your queries to create QM source members, then search through the source members. You could write a small CL program to get a list of all *QRYDFN’s, read the list and retrieve the source for each of them.
This is no guarantee that you will find everything, as the file name can be specified for the query at run time (from a command line or program), or possibly modified by using OVRDBF – and these file names maybe stored in a data area or physical file for example.
There’s a utility called RTVQRYF that uses MI code to extract details of files used in query objects.
I downlaoded it years’ ago from (I think) the News/400 website. It works a treat on v5.4, but we’re not yet at v6.1 so I don’t know if it works on that release as well.