If you haven't changed it, the unlock code is the last 4 digits of your phone number. If that doesn't work, dial *228 from your phone and follow the prompts to re-program your phone. This will reset your lock code to the last 4 of your phone number
Here's what I found on the Samsung website for that phone:
If this is in regards to the passcode to access the device, the default phone lock code of your phone is "0000" or "00000000" or the last 4 digits of the phone number.
If the default phone lock code did not work then we can do a reset on the phone. If a factory reset is necessary, please call Samsung Customer Support by phone at our toll free number 1-888-987-4357, between the hours of 7:00 a.m. to 9:00 p.m. Monday through Friday, and 9:00 a.m. to 6:00 p.m. Saturday, Central Standard Time.
I would suggest taking the device to your local corporate store, they have flash machines that they can plug your device in to and retrieve that unlock code information. Is there anything else I can help you with today?