Yes since you want to get collection of data matching to the input you are sending then you need to implement QUERY/Get_Entity_Set method. So that you get the collection of data as you are expecting.
Your URL will look something like this ->
/sap/opu/odata/sap/Z_COLL_PORTAL_SRV/fileRepositorySet?$filter=<Property_Name> eq 'XXXXXXX'