If I remember correctly the age is 13 or 14 years old.
Here's a link to an article on how to update an Origin Accounts:
How to update an EA Account to an adult account
https://help.ea.com/en-us/help/account/aging-up-an-origin-account-to-an-adult-account/
If you want more help with your account, please contact EA's Customer Service:
1. Click on the following link: https://help.ea.com/en/contact-us/ (once there make sure that your country is correctly selected in top left hand corner of Help.EA.com)
2. Find the affected game - in this case select either Origin or Sims 4
3. Select your platform
4. Select topic and issue.
5. Select a contact option. Please note that available contact options do depend on your country settings, time of day and the topic/issue you choose.