On Windows, files are stored by default in Documents -> BSD Concept -> Heredis -> Heredis Files.
However, you may have chosen another location at the time of creation, or moved it later.
To find the location of your file, open the software. From the home page, click on Search file on hard drive:
Heredis then searches your computer for any genealogy files it can open. The "Paths" column shows you the location of your genealogy file.