You can also right-click a file in the file explorer and select “Reveal in folder” (or similar—I forget the exact command title). This will take you to the file in the file system outside of Obsidian. From there it should be pretty easy to identify the root of the vault!
Edit: To be clear, in File Explorer (Windows) or Finder (macOS), your vault is simply the folder you selected when you first created it. I.e., a Vault is nothing more than a folder and its subfolders. You’re not looking for anything marked “Obsidian,” “Vault,” or similar. The contents of the folder you’re looking for will be identical to what you see in Obsidian.