Target class [App\Http\Controllers\User\UserController] does not exist code example

Example 1: Target class [UserController] does not exist.

Note: don't forget to import (use) your controller in the routes(web.php) file at the top. Like:
use App\Http\Controllers\PagesController;

Route::get('/',[PagesController::class, 'index']);

Example 2: Target class [App\Http\Controllers\EmployeeController] does not exist.

[PagesController::class, 'index']

Example 3: Method App\Http\Controllers\UserController::loadVie does not exist

Method App\Http\Controllers\UserController::loadVie does not exist