Error: Cannot find module in node.js

Firstly, this is not a duplicate. I have searched many questions of SO, but found no answer specifically to installing pagedown. This is my first module. I ran Node.js command prompt as admin, and ran this command.

> var pagedown = require("pagedown");

Here is the error log:

Error: Cannot find module 'pagedown'
at Function.Module._resolveFilename (module.js:338:15)
at Function.Module._load (module.js:280:25)
at Module.require (module.js:364:17)
at require (module.js:380:17)
at repl:1:16
at REPLServer.self.eval (repl.js:110:21)
at repl.js:249:20
at REPLServer.self.eval (repl.js:122:7)
at Interface.<anonymous> (repl.js:239:12)
at Interface.emit (events.js:95:17)

I am using Windows. Working directory: AppData\Roaming\npm\ <-- empty folder