npm can't find package.json

I think, npm init will create your missing package.json file. It works for me for the same case.

Update 2018

This is becoming quite a popular question and my answer (although marked as correct) is no longer valid. Please refer to Deepali's answer below:

npm init

Original Outdated Answer

I think you forgot to setup the directory for express:

express <yourdirectory>

Once you do that you should be able to see a bunch of files, you should then run the command:

npm install -d

Regards.

I'll be brief but deadly. :) install -d will not work for you. It's simple. Try

$ npm install -g express