Hi guys, how does one properly do npm cache clean?

Anyone know how completely clear the cache for npm? Basically I need to run webpack (using as a react npm package) and it used to work and now does not. Does anyone know how to properly npm cache clean and in which directory to do this?

Additionally I also read something about your environment PATH variable needing to be correct for cleaning cache and I somehow screwed that up. Under PATH it now seems to have combined two paths, one for my mongoDB and one for npm, both chained together with following value: