UsersController.php

<?php

public function register()
{       
      $user = $this->Users->newEntity();
      $value = $this->request->getData('username'); 
            
      if($this->request->is('post')) {
            $image_name = $this->request->data['profile_pic']['name'];
            $image_tmp = $this->request->data['profile_pic']['tmp_name'];


           $user_input_folder = WWW_ROOT.'img'.DS.'users'.DS.$value.DS;
           $destination = $user_input_folder.$image_name;

           if (!file_exists($user_input_folder)) {   //Checks file or folder exist or not
                if(mkdir($user_input_folder, 0777, true)){
                   $oldMask = umask(0);
                   chmod($user_input_folder, 0777);
                   umask($oldMask);
         

                  $this->request->data['destination'] = $destination;/// to store to destination field

                   move_uploaded_file($image_tmp, $destination);
                 } else {
                     pr("User input contains at least one illegal character, so can't create folder.");die;
                 }
           }
           
           $user= $this->Users->patchEntity($user,$this->request->getData());
             
          if($this->Users->save($user)) {   
             $this->Flash->success(__('User successfuly  added.'));
            return $this->redirect(['action' => 'login']);
          } else {
            $this->Flash->error(__('The user could not be saved. Please, try again.'));
          }
        }
        $this->set(compact('user'));
        $this->set('_serialize', ['user']);
    } 
?>

It will create notice on submit on if($this->Users->Save($user))

Notice (8): Array to string conversion [CORE\src\Database\Statement\MysqlStatement.php, line 39]
Notice (8): Array to string conversion [CORE\src\Database\Log\QueryLogger.php, line 92]

As of the moment the codes above can upload the actual image in the users directory but destination field in users table is empty