The game should not prompt you for a serial number, but if it does
try the following:-

7A84-EB75-7454-4282

Should that fail, try any and all of the following:-

0346-464C-7954-772L
A4FL-2BTO-E8WN-2ESU
93GI-44MP-80GI-B4MP
1EGO-E5AI-66SG-23AY
D303-CA11-8356-E548
7A84-EB75-7454-4282