That is the output that you see if you don't have any NVM versions installed but you have a system version installed.
Although it doesn't give the version of the system package but you can see what version you are using at any given time by using the command node --version
More precisely to query the system version; You should be able to see that using the command dpkg -s nodejs. (assuming you have a standard Ubuntu installation using apt and dpkg and have the standard nodejs package installed).
However if you're using nvm you should simply be able to install the version you want by running e.g. nvm install 16.15.1. The fact there is a system version shouldn't cause problems if nvm is working.
For what is perhaps the real question of why you have no NVM versions installed, or what version of node you are trying to restore; unfortunately there's no way of telling from the information provided.
PS: The command nvm ls-remote will give you a live list of all node versions available to nvm. For lot's more information about this you can refer to this stackoverflow question: How do I update Node.js?