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Can you please give more details of your need ? Do you need the product code of Windows 10 ? Or some another program ?
For laptops factory shipped with Windows, the serial number of the OS is actually within the BIOS menu, and not on the Windows 8/8.1/10 stickers under the laptop.
For a re-installation of the same version of Windows 8/8.1/10 as your system originally shipped with, you will not require to know the key. Windows 8/8.1/10 will use the key embedded in the BIOS.
The reason for the above is that it is one of the improvements Microsoft has made. All newly manufactured machines that came preloaded with Windows 8/8.1/10 will not come with the COA (certificate of authenticity). Instead, this will be embedded in the BIOS to avoid product keys from being compromised and OEMs will buy what they need.
You may find out some tools from the internet to help you view the product key (refer to Lenovo Forum peer-to-peer discussion https://forums.lenovo.com/t5/Windows-8-and-8-1/Where-can-I-find-the-product-key-on-a-preinstalled-version-of/m-p/932245#M1956). However, since the embedded key has only one purpose (to automatically activate Windows 8/8.1/10 on a single unique instance of hardware), it is uncertain if the key returned is definite, apart from being a collection of characters in a format that looks like a Microsoft key. Please refer this article also and try to find the product key.