Building services with Node JS on App Platform

I am using webpack to compile my node/expressjs application. When running the npm run build (which uses webpack), I keep getting the error ‘webpack not found’, even though I have all the webpack and webpack-cli dependency in my package.json

BUILD LOGS

backend                         | 18:59:31 > backend@1.0.0 build /workspace
backend                         | 18:59:31 > webpack
backend                         | 18:59:31 
backend                         | 18:59:31 sh: 1: webpack: not found
backend                         | 18:59:31 npm ERR! code ELIFECYCLE
backend                         | 18:59:31 npm ERR! syscall spawn
backend                         | 18:59:31 npm ERR! file sh
backend                         | 18:59:31 npm ERR! errno ENOENT
backend                         | 18:59:31 npm ERR! backend@1.0.0 build: `webpack`
backend                         | 18:59:31 npm ERR! spawn ENOENT
backend                         | 18:59:31 npm ERR! 
backend                         | 18:59:31 npm ERR! Failed at the backend@1.0.0 build script.
backend                         | 18:59:31 npm ERR! This is probably not a problem with npm. There is likely additional logging output above.
backend                         | 18:59:31 
backend                         | 18:59:31 npm ERR! A complete log of this run can be found in:
backend                         | 18:59:31 npm ERR!     /home/apps/.npm/_logs/2021-03-10T18_59_31_786Z-debug.log
backend                         | 18:59:31 building: exit status 1
backend                         | 18:59:31 ERROR: failed to build: exit status 1