@Simsun, @Sergei, unfortunately Pro Mode is not available anymore in Android Pie update for Galaxy S9, S9+ and Note9. A lot of users from different countries are complaining for removal of this functionality. All you can do is to report this issue to Samsung via Samsung Members app.
I have been asking for over a month now with no straight answer given to why the Pro video recording is missing.
I agree that before the update the camera on this phone was great, now it is useless.