How to find the C drive in Windows Subsystem for Linux

Simply cd into the /mnt directory/folder and you can will your system drives.

To access the c: drive from Windows Subsystem for Linux - WSL

Use this command to access the C drive on WSL:

cd /mnt/c/

According to the Windows Developer Blog

The WSL has access to your PC’s file system through /mnt// directories (or mount points). For example, your C: and D: root directories in Windows would be available through /mnt/c/ and /mnt/d/ respectively in the WSL