Why does my computer have 1TB storage but can't access it?

A couple years ago I bought a laptop (Thinkpad Yoga 14) and followed a professor's tutorial to change its system from Windows to Ubuntu for class. After I changed majors, I tried to change it back to Windows on my own and sort of (badly) managed to do so. However, I messed up and I can't access the majority of my laptop's storage. It originally had 1TB. Can anyone help me access the rest of it? I…

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