Npm proxy manager

Hi folks,

I could install and make some proxy hosts entries with the npm. This works fine so far.
Now i’d like to make a proxy host for the npm itself.
This always fails. How can I achieve this?
I use the port 4498, but it ends with following redirection:
https://npm.xyz.com:2000/?origin=host&app=nginx-proxy-manager&path=%2F

Kind regards