Here are the achievements for ORC.

-Witness (20) - Witness the beginning of the Raccoon City outbreak.
-Corrupted (20) - Complete the second mission of the USS campaign.
-Danger, High Voltage! (20) - Complete the third mission of the USS campaign.
-Rogue's Gallery (20) - Complete the fourth mission of the USS campaign.
-Betrayal (20) - Complete the fifth mission of the USS campaign.
-Down in the Labs (20) - Complete the sixth mission of the USS campaign.
-Outbreak Survivalist (25) - Complete all U.S.S. missions on Veteran.
-Raccoon City Cleanser (35) - Complete all U.S.S. missions on Professional.
-Success (30) - Complete all U.S.S. missions with an S Rank.
-Great Success (45) - Gain S+ on all U.S.S. mission on Professional/Veteran difficulty
-On A Roll (15) - Achieve a five kill streak in a Versus match.
-Skill... Or Luck? (25) - Achieve a 10 kill streak in a Versus match.
-Now That's G (15) - Collect three G-Virus Samples in one Biohazard match.
-No Sample For You (30) - Force 25 enemies to drop G-Virus Samples in Biohazard (lifetime).
-Supreme Survivors (20) - In Survivors mode, have all four players on your team Survive the game.
-Fallen Idols (30) - In Heroes mode, eliminate four Heroes in one game.
-Sampler (20) - Play at least one match in every Versus game type
-You Love to Hate my 98 (50) - Complete 98 Versus games
-Tongue Tied (10) - Kill a Licker that is grappling a Teammate.
-Like a Butterfly (15) - Kill 100 zombies with CQC (lifetime)
-Green Thumb (25) - Heal with 101 Green Herbs (lifetime)
-Down Boy (15) - Kill 13 zombie dogs (lifetime)
-These Will Do (10) - Purchase five weapons.
-Choices Aplenty (15) - Purchase 15 weapons.
-Quite The Collection (30) - Purchase all available weapons.
-One Trick Pony (10) - Purchase an ability.
-Feelin' Stronger Every Day (15) - Fully upgrade an ability.
-Look What I Can Do (20) - Purchase all abilities for one character class.
-Ready To Dominate (20) - Fully upgrade all abilities for one character class.
-So Many Choices (30) - Purchase all abilities for all character classes.
-Epic Standards (40) - Upgrade all abilities for all characters to its maximum level.
-Organic Shield (20) - Kill 5 enemies consecutively while using a zombie as a shield.
-Baker's Dozen (30) - Kill 13 zombified teammates.
-So Hot Right Now (15) - Kill 103 enemies with incendiary rounds (lifetime)
-Bloody Good Time (20) - Kill five enemies by causing Blood Frenzy in a single campaign game or multiplayer match.
-Up Close and Personal (10) - Kill five players in one multiplayer game with CQC Kills.
-Chaos Averted (5) - Kill an infected teammate with a headshot before they become a zombie in any mode.
-Like a Bee (20) - Kill (10) enemy players in one Versus game with CQC.
-A Gun by Any Other Name (15) - Kill an enemy with each weapon type including special weapons.
-Raccoon City Mascot (15) - Collect all seven Raccoons.

Is this for PSN Trophys too? looks like there are only six missions for the whole campaign

Yeah these are the same for the PS3 too.