Question: how to transfer files from usb to iphone?
Answer: Connect the USB drive and your iPad/iPhone (in iOS 8 or later) to your computer. Launch EaseUS MobiMover and navigate to "PC to Phone" on the main interface. ... 
Step 2: Windows File Explorer will open. Click the USB drive and choose the files you want to transfer to your iPhone. ... 
Here you can view the selected files.