I need to extract (download) from my iPhone 6 the data from third party application (mp3 files) to my Windows 10 PC. The data load to iPhone were from this third party application (`radio.kartina`) and were NOT using iTunes or any Apple applications.
Any applications I can download to iPhone and/or PC to have this access?

The USB connection gives me access to photos (and videos) only, but I need to get these mp3 files from iPhone 6 to my Windows 10 PC.

I would appreciate any help - name of application to use or detail instructions. Regards, Simon.