How do I unlock new zombie maps?

Do as chris says up until you get to the PC then type in 3ARC UNLOCK and it will unlock the last 2 maps included with the standard version of the game for online and local use.

I dont know where people are getting this 2 zombies maps for 3arc unlock there are 3 zombie maps 1 that is already unlocked when you play the game then "FIVE" which is unlocked from campaign or 3arc unlock then dead ops arcade which is doa on the computer

There was two games that you could buy one is just the game and comes with everthing and that inludes zombies, but there was also a game that was more like for me it was 75 and the game comes with codes and you put them into the computer

You could beat the campaign and go through the credits and get "Five", and you have one zombie map unlocked already (Kino Der Toten), but if you want to get all maps go to the main menu. When there, press LT,RT,LT,RT,LT,RT or if you're on PS3, L2,R2,L2,R2,L2,R2 rapidly until you get out of the chair. When you're out, walk around until you find the computer in the back of the room. Use it, and type "3ARC UNLOCK" and it will say "Cheat Unlocked!" on the computer screen. Then go to zombies and there. you have all of them

The 3ARC code unlocks all intel files disabling the achievement for it but DOES NOT unlock any zombie stuff.

When you first play, "Kino der Toten" (Theater of the Dead) is available under the zombies menu.
"FIVE" is unlocked when you finish the campaign, then available under zombies.
"Dead Ops Arcade" is unlocked by escaping the toture chair in the main menu & entering DOA on the computer in the room, will then be available under zombies.
"Zork" (a text based game from 1980, not zombie map) is unlocked by typing ZORK on the computer.

There are 4 more zombie maps that came included on a free to download card with the harderned edition of the game as well as a Capt. Woods avatar uniform. These were the four maps from World at War.

However your question is what to do to get to round 10 on "Kino der Toten" which is to just...
KILL KILL KILL!!!!!!!!!!!!!!!!!!!!!
I can get to the stage (in single player since I don't have LIVE) in 4-6 rounds & can last until 15. Here are a few tips:
1. Rounds 1 & 2 just stab everthing to save ammo & maximise points. 10 poist for a hit or barrier repair, 50 for a kill, 100 for a headshot kill, 130 for knife kill.
2. On each round the number of stabs to kill a zombie is equal to that of your round number, round 1 = 1stab, round 2 = 2 stabs & so on.
3. On round 3 start to epty a clip into a zombie before stabing to kill in one go.
4. Always try to get to the random weopon crate as soon as possible.
5. Recomend going through the doors under the stairs to make you way to the stage

6. If playing single player the quick revive drink dispenser will work without the power being on & as such being in single player will make you revive on your own. Can only be used 3 times.
7. Weopon upgrade machine if you go through the teleporter for 5000 points.
8. If all players in a match go through the teleporter, all zombies will converge in front of the stage.
9. If you hold onto your starting handgun until you get to the upgrade machine, you will get a dual wield explosive shot handgun.
10. The zombie dogs will first appear on round 6 & the gas zombies the next round after activating the power.
11. When the power is back on the location of the weopon crat is highlighted on the maps.

I have only included the information about the other maps to say that the others where answering the wrong question for that is not what you asked but to still help you in unlocking them