There's no way to specify search parameters on the mobile app when performing a database search. You can, however, change the search parameters for individual libraries which will specify search results when searching the database. To do this, open the library, select the 3 dot menu, and select settings. Then scroll down to the bottom of the list and select search settings.
You can also narrow searches to a specific library by performing a search while in the library.
If you have the Momento Database Pro desktop PC app, you can specify which library to search in when searching the database.