I bought hitman SteelBook edition, and the redeem code of the (The complete first season) DLC is 18 digits, which can not work on PSN account for PS4.
Is it the requiem pack and bonus episode you want to redeem?
You need to contact square enix for that. I dont think IO has codes for that edition
If you search hitman steelbook digits redeem in google you can find some threads and solutions to your problem.
If they dont answer you, contact IO support mail or @Travis_IOI the details and that square doesn’t answer you so that could maybe make the process go quicker.