This step by step guide with images covers how to transfer files between iPhone and Mac with a USB flash drive as well as offering a few alternate options.

Quickly transfer files between your devices using the iXpand Flash Drive Luxe, which features both USB-C and Lightning connectors.

How-To How to format a drive for Mac, and which format to use Learn the nuances of file formats to get the most out of your flash drives.

The drive took essentially the entire contents of my new 12-inch MacBook and in a few seconds had successfully pasted copies of the files into its 32GB storage.