Can't activate my razer headphones

So i bought this headphones some years ago and as soon as i bought them i downloaded and used 7.1 sorround ,my headphones by the way are the "Razer Kraken Pro V2" green. Since i bough them a long time ago i don't have the key that come in the box anymore , i threw it away cause i thought i would'nt need anymore the activation code after i registered my product , i thought id just download and i could just use i t back again, but since i bought my new computer i havent been able to use it cause it always ask for an activation key and i dont know where to get it from. P/N:RZ04-02050600 S/N:HN1823D05351720