How to access to non-synced one-drive files on non-accessible windows?

I have windows 8.1 running on MacBook Pro laptop. The problem is that when I boot into windows, the screen is stuck on welcome page and does not go to the next page where I can enter my pin code. I tried every thing to solve this problem but nothing worked. Now I need to transfer all my files in the Windows system to external hard drive including one-drive files. Some files on my one-drive storage have not been synced for unknown reasons, so they do not show up on my Microsoft account. Are these files still accessible? If so, how can I access them and all other files in the Windows system ?