How can I transfer my mobile photos into a USB flash drive?

I have an iPhone 7, I'm trying to transfer my pictures from my phone into a USB flash drive. How I do that?

Certainly not an expert here, but one would think that you would have to upload them to your cloud, download them to a iPad or computer and saved them to a USB drive

IPhone 7 supports OTG, so use an OTG cable. No need for Cloud, email, nothing. Don't even need a computer.

We don't know which "USB flash drive" you are using. You need to use an external memory device that is designed to do what you want… The iPhone7 has no USB port - it has a Lightning connector port.
https://www.apple.com/...e-7/specs/
Scroll down to "External buttons and connectors".

I prefer those using a memory card like
https://www.bhphotovideo.com/...eader.html

Without purchasing anything, you can simply send the photos to yourself or store them in the cloud. Then download them onto your computer can copy them to your USB drive.

If that's too hard then you would need to buy a flash drive that is compatible with iPhones.

Open the Photos app on your computer and you'll find all the photos. Select all and copy. Then go to your USB on your computer and click paste. Usually works for me.

After the copying process is over, check the memory the photos are and make sure the same memory is in your USB (for example if the photos are 25.6 GB on your phone, if should be the same on the flash drive). Do that to make sure all images have been copied.

And you're done! Usually works for me. Hope I helped xxx

Plug phone into computer (assuming Windows here), check under the main folder (depending on which version of Windows you have) & access the pics there. From there you could copy/paste to the flash drive.

1) copy files from the mobile to the computer
2) copy files from the computer to the USB