My first Multipla also came with no radio code. I did however have the service book which named the original seller (Fiat Garage).
Luckily the dealer had made a note of the radio code, and was able to tell me it over the phone.
When I bought my second Multipla, I wasn't so lucky- no code, no record at dealer. So I found a bloke on Ebay who would supply the code if you sent him the radio serial number. Cost £1.50.
I understand there is software available to do the same thing, but probably quicker to use Ebay.
hth
Neil