Haven't done it with USB flash drive but I would be very surprised if
this doesn't work.
You need the target USB flash drive exactly the same size ( with exactly the same number of sectors) or just larger.
-----------------------------------------------------------------------------------------------------------------
Alternatively you can just duplicate the directories to another flash drive and restore the boot loader. Copying commands for the files do not touch the boot loader hence the need to restore the boot loader which resides in the boot sector. Methods of doing it are available at the last link of my signature. PCLinuxOS uses Grub so it should be Task B4 or B5.