Transfer files to your android/Fire devices using any web browser. Amazon Appstore version supports transfers to both Internal Storage, External Storage, A limited replica is available on Google Play that uses Storage Access Framework and requires no permission but can only send to Downloads folder.
The app has been removed by us from Google Play, regarding the apk and where it can be found please refer https://github.com/visnkmr/wfm/issues/222#issuecomment-1848265970