the -get argument is intended to start the transfer queue as if you were manually pressing "transfer queue" and is not valid in the context of the example you attempted above. 
 
try something like 
Flashfxp.exe -fxp Site_Name\file.txt;Site_Name2\path\file.txt 
 
if you're transferring a file you need to provide the filename for the target as well.
		 
		
		
		
		
		
		
		
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