If, as I assume, you have not kept the original package (where the puk is indicated - usually on the piece of plastic/card from which you cut out the sim card), I don't see any alternatives but to contact the helpline (190 from Italy - +393492000190 form abroad); they will ask you to provide them with alll your details (DOB, address, etc.) before providing you the PUK number.
Alternatively, if you have already registered with
www.190.it (and remember that password!) you will find the puk code in the "fai da te" section.
My Phones: Nokia 6230 - Nec N343i - Nokia 6230i
My Sims: Wind IT prepaid (+ Voda IT postpaid corporate phone)
Prepaid Sims: WORLWIDE: Riiing, UM+ - IT: Voda, Wind
Deceased Sims: WORLWIDE: Hop - NZ: Vodafone - FR: Bouygues - IT: H3G - US: T-Mobile