Apologies, I didn't read your post properly. Backing up a NAS to a PC, eh? How unconventional.
You can achieve what you want to do with a simple batch file. Like this:
Then you can have task scheduler run the batch file whenever you want, and it can also wake your PC to run the task.
:: Delete old destination backup folder
RD "Y:\Backup" /S /Q
:: Wait until folder has been deleted
TIMEOUT /T 1
IF EXIST "Y:\Backup" GOTO waiting
:: Copy source backup folder and files to destination
XCOPY "Z:\Backup" "Y:\Backup" /E /I /H
I tested this using two network drives, one as source, one as destination, and it works fine.