Help installing Windows 8 then upgrading to Windows 10

Hello, I am new here. I had queries about installing windows 8 then upgrading my PC to window 10. Problem here is that my pc was bricked once, I guess some months before, so I took it to a shop for reinstallation of windows. Unfortunately, the shopkeeper removed the original version (Win8Home) and installed a pirated version of Windows 8.1 ( which was professional ). I came to know about it when I tried to update it to Windows 10. I had windows 8 home on this pc initially. Now I have retrieved the MSDM key and am thinking to download ISO of both 10 and 8 and using the same key to activate when I clean install windows 8.The problem here is that I'm unable to find ISO of Win 8. Here is the link " https://www.microsoft.com/en-in/software-download/windows8ISO" which comes up when I search windows 8 ISO and the name of the page says so even. But it starts to download windows 8.1 ISO. Please tell me if i can use the OEM/MSDM key to activate Windows 8.1 and then upgrade it to windows 10.
Please tell me if it won't work and suggest an alternate.
Any help is appreciated.
Note that I had upgraded once to Windows 8.1 using the MSDM key previously.
Thanks in advance.
Regards.

 

https://support.microsoft.com/en-us/help/12440/windows-10-activation

 

Thanks man ! Just needed to ask one thing. If I download ISO from this link " http://www.microsoft.com/en-us/software-download/windows10ISO" and then enter my product key, will it work on a PC which is not activated prior to installation ie using posted build ? 'cuz I'm not sure if this ISO is of which build.
Also, this key is OEM one, that in bios.

 

I'm not sure, but chances are that Windows 10 will pick up your key from BIOS.

 

Okay, trusting you I am taking chances of wasting another 4 GBs of my internet . Let's hope for the best. I'll get in touch when I'll be back from school and have tried installing it.
Thanks again !

 

Use the schools internet maybe? I mean, if you have a data transfer cap yourself.