First, if you have an older version then 4.2 Blender won't prompt you to copy preferences.
Second, You need to know where the user folder is located. Replace [Blender Version] with your version number. In this case 4.3
For Windows: %appdata%\Blender Foundation\Blender\[Blender Version]
For Mac: /Users/$USER/Library/Application Support/Blender/[Blender Version]
For Linux: $HOME/.config/blender/[Blender Version] or $XDG_CONFIG_HOME/blender/[Blender Version]
Third, option1: to get the option on splash screen, double click config folder then delete userpref.blend file
option2: Go into previous version of blender's folder and copy and paste everything in there to the 4.3. Note: If it was older then 3.3 you may have to click file->Defaults->Load default settings and then click file->defaults->Save startup to fix the icon and UI layout problems.