If you want to format a USB memory stick to remove all of its contents at once, then please follow the instructions below.

In 'Computer'/'This PC' right mouse/trackpad click the USB memory stick you want to format, then click 'Format'

Click 'Format' for format the USB memory stick, to delete all of the files and folders on it.

If you are happy to delete all files and folders on the USB memory stick, click 'OK' to confirm the formatting.

If you have any files or folders open that are on the USB memory stick, you may get an additional warning.

If you have, close them first, then click 'OK'.

If you haven't, click 'OK'

NOTE: Just having 'Computer'/'This PC' open displaying the USB memory stick icon may give this warning, in which case click 'OK'

Click 'OK' once the format is complete

Now the formatting is complete, click 'Close'.

The USB memory stick will now be empty, ready for use.