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.