Error : cannot find module 'gulp-concat'

ionic $ module.js:339
throw err;
ive tried doing npm install gulp but its still coming up with this error my app is completely blank on the browser so im guessing its this thats causing me problems any ideas how to fix it

Error: Cannot find module 'gulp-concat’
at Function.Module._resolveFilename (module.js:337:15)
at Function.Module._load (module.js:287:25)
at Module.require (module.js:366:17)
at require (module.js:385:17)
at Object. (/Users/Jess/Downloads/Social-Network-Mobile-App-master/gulpfile.js:4:14)
at Module._compile (module.js:435:26)
at Object.Module._extensions…js (module.js:442:10)
at Module.load (module.js:356:32)
at Function.Module._load (module.js:311:12)
at Module.require (module.js:366:17)

Try install: sudo npm install gulp-concat -g
to install gulp-concat globally.

ive fixed the issues but the app still has a blank screen in the browser and its not coming up with any errors.