Hi @Georgette,
in Win 10 go to Apps and Features (guess it’s called like this in English), scroll down to Nik Collection and uninstall it.
Instead, you might re-install Nik 3 – see here Issues with Nik4 - #8 by Wolfgang
To get rid of Nik 3 and 4, just uninstall die Nik 4 Version. It will uninstall Nik 3 as well.
Wolfgang