You will have to look at the source code for that program.
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Much depends on your having programmer authority and some knowledge
That is, methods to determine source of data would depend on
1) you having programmer authority
2) you having access to the source code
3) your level of knowledge and expertise
Otherwise you are probably going in the right direction. You have a method to determine the most likely files, although a file doesn't have to be on that list to be a source of data.
You will have to search files for data that matches what you're seeing on the screen. and what you are seeing maybe from one or more fields in one or more files.