Update Engine versions

Hello,
the latest version of Rocket.Chat uses Node: 8.11.4, NPM: 6.4.0
my versions are Node: 8.9.3, NPM: 5.5.1

I have updated my versions by running these commands:

n 8.11.4
npm install npm@6.4.0 -g

My question is, is it enough or I need do something more?

Sounds like n isn’t updating nodejs. Try typing: which node

/usr/local/bin/node
also I have checked this:
# node -v
v8.11.4
# npm -v
6.4.0
# nodejs -v
v8.10.0

how should I update nodejs?

Do you type node main.js or nodejs main.js to start Rocket.Chat? If you use the former… no need to do more

I start my Rocket.Chat with node main.js