Delete Market from Plugins.

After you make these changes, "Market" tab and "Download more themes at Market" will disappear from the Plugins section.

Open the following file:

index.php
oc-admin/themes/modern/plugins/index.php

Locate and remove this code:

index.php
<li><a href="#market" onclick="window.location = '<?php echo osc_admin_base_url(true) . '?page=market&action=plugins'; ?>'; return false; "><?php _e('Market'); ?></a></li>

‚Äč

Open the following file:

add.php
oc-admin/themes/modern/plugins/add.php

Locate and remove this code:

add.php
<div class="flashmessage flashmessage-info flashmessage-inline" style="display:block;">
<p class="info"><?php printf( __('Download more plugins at %s'), '<a href="'.osc_admin_base_url(true) . '?page=market&action=plugins">Market</a>'); ?></p>
</div>