This thread is rather borderline, so please remember to read the forum rules before posting. Piracy discussion is not condoned here.
Nevertheless, since there are legitimate reasons to want to backup/restore your save file, look into Rudolph's NDS Backup Tool. The wifi version lets you use just a slot-1 device (involves setting up an FTP server on your computer) while the slot-2 version simply interacts with a slot-2 device.
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