The number you're looking for is FIVE.

Cosmic Pioneer 2RVQE-?RNL8-24I6J
Sky Hawk 6?64Z-EA5W2-FQGV4
Gevaudan 7F?6Z-795WB-DYNHA
Plancon: Space Conflict DC?HZ-VN7TF-TEXEA
Plancon: Space Conflict DNH48-A4QKH-J?TR7
Dino Run DX 4PV86-L?34M-3YJBY
Mobile Astro 2?M7V-8NL67-W7XMX
Case #9 0W4QA-2QV6F-DPA?W
Project Mercury 2?76I-059YR-9F8KN
Iron Sea Defenders ?3QBH-JLPZL-A083V
Iron Sea - The West Coast ?3P5D-ADRJF-6MXFV
Iron Sea - Lost Land ?27Z7-JY4VL-X3BZR
Iron Sea - Soundtrack 4ZWYB-E6?X4-RFEI2
Darkstone 7MREI-?XK7G-WV63H
Pocket Kingdom A44K3-78Q8Z-?ZEKH
Red Game Without a Great Name 4ZL?2-0J74J-G8JD2
Doodle Kingdom ?3H3T-XGJXV-X7LH2
Starship Titanic JE6ZI-00KN?-8ZDJT
Black Moon Chronicles 7EQ9I-?8KJJ-V9A62
Caveman World: Mountains of Unga Boonga 3DAT3-DCA8D-4GM?I
Portal of Evil: Stolen Runes Collector's Edition 4XJAD-2?AY7-8ATDJ
Last Horizon 4?73Y-BEMBQ-Q0HJM
Security Hole 8VF7?-CAY7Z-33AWL
Security Hole 8TL70-CMPH8-L?TAB
BOX align 6TG0T-XBVBN-?HLEZ
Market Tycoon 6MBAJ-676VY-L?AYQ