Thank you for posting your inquiry here in Microsoft Community, FilipeSilva06.
Do you mind asking, what happened to your Surface Keyboard? Here are some ways to find the serial number of your keyboard:
If you prefer to talk to the PC accessories team, you may reach them through these steps below:
1: Go to Contact Us - Microsoft Support (Make sure you are signed in with your personal Microsoft account)
2: Sign in with your personal Microsoft Account
3: Click on Get support
4: Enter a brief description of the issue on the Describe your issue here... box
5: Click on Get Help
6: Click on Contact Support below
7: Under Product and services, select Other Products
8: Under Category, select Microsoft Accessories
9: Click on Confirm
10: Chat with support agent and Provide your phone number options should appear. Choose one then provide the details asked.