Product key Windows 10 Trekstore?

I recently upgraded a trekstore surfbook A13B because my laptop broke down. Now I have to enter a product key but I can't find it in the manual. Can someone please tell me where I can find that.

If Windows 10 was already installed on the device, then you can skip the entry of the product key. (The button / link is hidden on the screen, unfortunately.)

If not, then you should contact your salesperson and ask for the license key - if it was included in the purchase.

There's a code for the win.

If it's a legal win, then call Microsoft support. They give you a new code and help you.