Check that your iPhone supports the file app and external storage
Use a compatible USB flash drive or a Lightning/USB-C adapter
If your iPhone has a Lightning port, use a Lightning to USB adapter or Lightning to USB 3 Camera Adapter
If your iPhone has a USB-C port, connect the pendrive directly or use a USB-C adapter if needed
Plug the pendrive into the adapter
Connect the adapter to the iPhone
Open the Files app on the iPhone
Tap Browse
Look for the pendrive under Locations
Tap the pendrive to access its files
Copy, move, or open files as needed
Safely eject the pendrive before unplugging it
If the pendrive does not appear, try using a powered adapter or a different drive format compatible with iPhone