You will need an 8GB flash drive and another computer to set up the flash drive for Windows 10 installer.
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And hopefully the mSATA SSD installed inside the Surface has not gone faulty as that is a PITA to replace, really hard to separate the screen without damaging / cracking it.
Sounds like no operating system is installed on there. You will need to create installation media using the 'windows media creation tool'
You can download it from here:
https://www.microsoft.com/en-au/software-download/windows10
You will need an 8GB flash drive and another computer to set up the flash drive for Windows 10 installer.