Use APKPure App
Get Usb Flash Drive File Transfer old version APK for Android
Usb Flash Drive File Transfer allows you to transfer files with NO ROOT [OTG]
Usb Flash Drive File Transfer allows you to transfer files without the need of having a rooted Android phone. Just drag and drop files between the upper grid (your phone) and the lower (the USB Flash drive device) to transfer files and entire folders between them.
USB Flash Drives must be formatted to FAT32.
The app is still in a early version so I would appreciate any suggestion and comment.