How get all pages in plugin for admin

    public static function getSubscribedEvents() {
        return [
            'onPluginsInitialized' => ['onPluginsInitialized', 0],
        ];
    }

    public function onPluginsInitialized(): void
    {
        // Don't proceed if we are not in the admin plugin
        if (!$this->isAdmin()) {
            return;
        }

        $basename= $this->grav['uri']->basename();
        $uri = $this->grav['uri'];
        $config = $this->config();

        $route = $config['route'] ?? null;
        $route == $uri->path();
        $this->grav['debugger']->addMessage($route);

        if ($basename == 'contacts') {
            $this->enable([
                'onPageInitialized' => ['onPageInitialized', 0]
            ]);
        }
    }

    public function onPageInitialized($event): void
    {

        $this->grav['admin']->enablePages();   

        $grav = Grav::instance();
        $this->grav->fireEvent('onPagesInitialized',$event);
        $this->grav['admin']->grav['pages']->init();
        $page = $this->grav['admin']->grav['pages']; 

        $this->grav['debugger']->addMessage('-----------------------------------------');
        $this->grav['debugger']->addMessage($page);
        $this->grav['debugger']->addMessage('-----------------------------------------');

        //$paths = $event['pages']->find('/', true); - null
        //$paths = $event['pages']; - null
        //$page = $this->grav['admin']->grav['pages']->find('/'); - OK
    }

public function onPagesInitialized($event): void
{
    /** @var Pages */
    $pages = $event['pages'];
}

if ($this->isAdmin()) {
    $this->enable([
       // Put your main events here
       'onPagesInitialized' => ['onPagesInitialized', 0],
    ]);

    return;
}

<?php
namespace Grav\Plugin;

use Grav\Common\Plugin;
use Grav\Common\Page\Collection;
use Grav\Common\Uri;
use Grav\Common\Grav;

class dataJsonPlugin extends Plugin
{

    public static function getSubscribedEvents() {
        return [
            'onPluginsInitialized' => ['onPluginsInitialized', 0],
        ];
    }

    public function onPluginsInitialized(): void
    {
        // Don't proceed if we are not in the admin plugin
        if (!$this->isAdmin()) {
            return;
        }

        $basename= $this->grav['uri']->basename();

        if ($basename == 'contacts') {
            $this->enable([
                'onPagesInitialized' => ['onPagesInitialized', 0]
            ]);
        }
    }

    public function onPagesInitialized($event): void
    {
        $this->grav['admin']->enablePages();   

        $pages = $event['pages']->all();
        foreach ($pages as $page) {
            dump($page->header()->title);
        }

        exit();
    }

}

if (!$this->isAdmin()) {
   return;
}