Sim card voucher #

Question

I bought a phone to replace the handset for the one that i had and it came with aprepay card, i wanna use the prepay card now but it is telling me that i need the secret code from my voucher and i dont have that anymore because i trough it away..
anyway how can i refill this fido sim card or how to get that #???
ps. i dont rememebr the phone # designated for that sim card.

Rick