The 16 digit serial code

game codes are 20 digits long DLC bonus content is 16 digits long you should have another piece of paper perhaps how to install the game leaflet on the back of that the 20 digit game code should be there

if you have invaladited your code you will need to contact CS

20 digit codes

1.     Go to http://www.thesims3.com and make an account if you do not already have one.  If you have an account, skip to step 3.
2.     When making an account, enter your serial code for The Sims 3.
3.     Once you are a registered member of the The Sims 3 website, login to your account so that you can then register any other expansion packs or stuff packs that you own to your account.
4.     Click on the My Page tab.
5.     Then click the My Account tab.
6.     Click on Register a Game.
7.     Enter the product code for the expansion pack or stuff pack.
8.     Click the green Register button.

16 digit codes

1. Go to thesims3.com and log in with your account
2. Go to your account page: https://store.thesims3.com/myAccount.html (site will ask for your password again) 
3. Click on Redeem a Code 
4. Enter the 16-letter code, accept the Policies and click on Redeem
5. Go to your purchase history to download the world (make sure your game is updated to the newest version)

if in the event you need to contact CS

1.https://help.ea.com/en/contact-us/
2.Click on the orange NEXT button
3.Select a platform
4.Click on the orange NEXT button
5.Select a topic and describe your problem in a few words
6.Click on the orange NEXT button
7.Click Chat Now to chat with a Game Advisor


guide on how to contact CS

http://answers.ea.com/t5/Beta-Archive/How-to-contact-a-Game-Advisor-using-the-new-EA-Help-page/td-p/2161281