How to install Windows OS on my Razer Blade Stealth 2016

Hi, How do I get a copy of Windows OS and key of my Razer Blade Stealth 2016? My NVME SSD is not being recognized by my laptop and I have to replace it. I need to fresh install Windows and can't open my previous SSD. Here are my questions: 1. Where to download Windows OS? 2. Where to get the Windows License Key? 3. Is there anything I need to do after installing a fresh Windows Key on a new SSD? Thanks in advance. FYI, I bought a Transcend PCIe SSD 110S 256GB for the replacement.