Error Cannot find module 'koa-passport' when npm start

[WahidinAlambiyah]

got error messages like this

server@0.0.1 start E:\React Native Testing\ReactNativeSampleApp\server
node --harmony server.js

module.js:557
throw err;
^

Error: Cannot find module 'koa-passport'
at Function.Module._resolveFilename (module.js:555:15)
at Function.Module._load (module.js:482:25)
at Module.require (module.js:604:17)
at require (internal/module.js:11:18)
at Object. (E:\React Native Testing\ReactNativeSampleApp\server\server.js:4:18)
at Module._compile (module.js:660:30)
at Object.Module._extensions..js (module.js:671:10)
at Module.load (module.js:573:32)
at tryModuleLoad (module.js:513:12)
at Function.Module._load (module.js:505:3)
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! server@0.0.1 start: node --harmony server.js
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the server@0.0.1 start script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.
npm WARN Local package.json exists, but node_modules missing, did you mean to install?