node + plesk + ssl : how to make them run together?

My client's websites runs a ssl generated by PLESK.

I used to run node.js with SSL thanks to:

var ssl = {
    key:  fs.readFileSync('/etc/letsencrypt/live/mysite.com/privkey.pem'),
    cert: fs.readFileSync('/etc/letsencrypt/live/mysite/cert.pem')
};

But I have no idea where PLESK did create these 2 files.

I tried with:

> /etc/ssl/certs/ssl-cert-snakeoil.pem
> /etc/ssl/private/ssl-cert-snakeoil.key

With no success.

Any idea on how to run nodejs with SSL generated by Plesk ?

via yarek