If you don't have Win 10 install media, can you create it after reading -
https://www.microsoft.com/en-gb/software-download/windows10You don't need a product key.
As you can't open This PC then you will be unable to perform a repair install, so we'll try it this way.
Boot up with the install media - if using an USB then insert that before tapping F12 as you switch on to select that option with the cursor keys and press Enter.
When the install media has loaded, navigate to the Install screen and click on Repair your computer/Troubleshoot and select Command Prompt.
At the prompt enter
bcdedit |find "osdevice"For clarity that is a Pipe symbol before find and is the uppercase of \
Using your partition letter instead of the x I have exampled, enter -
dism /image:x:\ /cleanup-image /restorehealth
You can usually disregard what it says about the scratch directory and wait for the cmd to complete.
Follow that with, again using your partition letter instead of the X I have exampled, enter -
sfc /scannow /offbootdir=X:\ /offwindir=X:\Windows
Enter
exit to close the cmd window, remove the install media and restart to see if they have resolved the problem.