If the extraction yields a decrypted folder (not a clean NSP), you need these applications. Warning: These require Python or specific runtimes.
NSP (Nintendo Submission Package) is the for the Nintendo Switch. It is essentially a digitally signed container used by the Nintendo eShop. rar to nsp converter
You cannot "convert" a suitcase into a shirt. You must the suitcase to get the shirt out. If the extraction yields a decrypted folder (not