how to set a new admin Password of the existing admin user using MySql query?

UPDATE admin_user SET password = CONCAT(SHA2('cryptkeyPASSWORD@#$123', 256), ':cryptkey:1') WHERE username = 'USERNAME';

You can find the crypt key in the below file:

Magento_Root/app/etc/env.php

'crypt' => [
      'key' => '82df4fe20ecf9af24614a2f6b76ac7b6'
],