Hi @fernandoch,
You can copy the entire dir /etc/letsencrypt/ and restore it on your new server.
Old server (as root):
tar zpcvf backup_etc-letsencrypt_2018-Nov-20.tar.gz /etc/letsencrypt/
Now transfer the file to the new server.
New server (as root):
tar zxvf backup_etc-letsencrypt_2018-Nov-20.tar.gz -C /
And you have all the certificates, renewal confs, etc. on your new server.
certbot will use the information saved on renewal conf files /etc/letsencrypt/renewal/* so if the paths to your webroot etc. are the same, you should have no issues, if the paths have changed then you should modify them on the renewal conf files for all your domains, but well all this depends on how you issued your certificates... (using certonly, webroot, apache plugin, nginx plugin, etc.)
Cheers,
sahsanu