I know you don't want to lose your important data.
I highly recommend putting the hard disk in an enclosure and connecting it to another PC and copying all important data to an external storage device.
Since you had Windows 10 installed that means you Windows 10 license activation key is safely stored online at the Microsoft licensing servers.
You will need to download the Windows 10 Media creator and use it with a USB flash drive (4 GB minimum storage capacity) to create installation media. Use the following URL to get the Windows ISO installation media creator.
https://www.microsoft.com/en-us/software-download/windows10
Once you have done that, boot to it and install Windows 10. It will be activated once you go online.
All required drivers for Windows 10 are at the following HP support web page.
http://h20564.www2.hp.com/hpsc/swd/public/readIndex?sp4ts.oid=5230511&swLangOid=8&swEnvOid=4192
Install the chipset and IMEI drivers first, then install the graphics driver software.

I am not an HP Employee.
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For laptops or desktop PCs, use the Fn+Esc keystroke while logged into Windows to locate the Product number (SKU)