I am unable to find Express.js,Node.js and also MongoDB

please tell me where i find it.

it will be in your computer try accessing it with powershell terminal if still not coming try accessing it with powershell administrator

No it not about installation

I want to learn node. Js , express. Js and database mangoDB where do I find it codechef

you should learn it from another source like w3 school

First of all you will have to learn it.
For setup first download nodejs then I’ll be able to share you the further information.