So you upgraded 7.4 to 8.0? You only run 1 instance of PHP then?
Exactly where are you looking in the file editor?
There is almost no difference between a php.ini between 7.4 and 8.0 if I'm not mistaken. However, in the options.conf the setting for the php.ini file has to be php_ini=yes to get an ini file.
If already one exists, it probably won't get overwritten. If you would to backup and remove it and build php again, a new one will be created.
But if you changed things in the one from 7.4 you have to re-create those changes in the newly created php.ini for php 8.0.