This short guide explains how to upgrade an existing installation of VMWare ESXi 7.0 to upgrade 3L
As pre-requisite you need to have too access and either insert the commands directly or via an active SSH connection.

esxcli network firewall ruleset set -e true -r httpClient
esxcli software profile update -p ESXi-7.0U3n-21930508-standard  -d https://hostupdate.vmware.com/software/VUM/PRODUCTION/main/vmw-depot-index.xml 
esxcli network firewall ruleset set -e false -r httpClient