How can i get master key?

I am not sure I understand, do you mean the Windows key?

If you are asking for master password, which can be generated from system service tag, it will be a paid service.

If you are asking for Windows license number, it's a pre-activated OEM volume license, which has no value to any users.  license key is hard coded in motherboard firmware.  

@JOcean​ I bought it recently and it was said that it is applicable for intel gamer days offer where I would recive 2 games. To redeem thi se games master key is required. 

@Fury_l​ I believe that master key was to come from Intel. This web page may help but you may have to contact Intel support or Dell sales/support or both.

This information was found on Bing and it may help also:

To get the Intel Gamer Days Master Key, you need to follow these steps:

1. Go to softwareoffer.intel.com and sign in or create an account. Please note that your phone number is required for account verification and access.
2. Once your account is verified, log in and enter your Master Key by November 30, 2023, 7:00 am Central Time to claim your software.
3. Agree to the Offer Terms and Conditions and complete the short survey.
4. Select and download the available software products.

Please note that the Intel ® Gamer Days offer has officially ended and the offer is no longer available 1. If you purchased a qualifying Intel ® device between August 24- September 5, 2023, you have until November 30, 2023, to enter your Master Key. Nightingale will be available to download and play on February 22, 2024 1.