How do I delete ._ on mac USB file names

Trust me it works. The issue is that you failed to recognize that my use of /Volumes/MyFlashDrive was to be replaced by your own path string by dragging and dropping your mounted USB stick onto the Terminal and then pressing return.

You type only the following with a trailing space:

dot_clean -m 

and then drag/drop your USB stick from the Desktop onto the Terminal behind the preceding command, and then press return. If there is any white space in the drive name, you need to enclose it in double quotes.

You can open Finder and use the following keyboard shortcut to toggle hidden items on or off. Please proceed with caution. Deleting hidden items may impact software functionality.

Shift-Command-Period (.)

Here is an article that includes more keyboard shortcuts.

• Mac keyboard shortcuts - Apple Support

Alternatively, you can erase and reformat a storage device in Disk Utility.

Use the following Apple Terminal command-line with the specific name of your mounted USB flash drive:

dot_clean -m /Volumes/MyFlashDrive

This will remove all ._ files only.

The dot_clean utility is what I use for my own USB sticks.

Another way for 10.13...

Find Any File...

http://apps.tempel.org/FindAnyFile/index.php

Hold Option or alt key when selecting Find to Find All.

In Find Items choose that USB drive, then choose Name>Begins with...

._

In the resultant list Select All then Delete.

If you're averse to the Terminal then this

https://apps.apple.com/us/app/blueharvest/id739483376?mt=12

will do it too.