How to make query in Yii 2 - php

Question

I want to make a code user id with my style, but i confuse to make it in Yii 2.
Can you help me, how write the query like this code below in Yii 2.
This is my code:
$sql = "select * from `$tbadmin` order by `kode_admin` desc";
$q = mysql_query($sql);
$jum = mysql_num_rows($q);
$kd = "ADM";
if ($jum > 0) {
$d = mysql_fetch_array($q);
$idmax = $d["kode_admin"];
$urut = substr($idmax, 3, 2) + 1; //01
if ($urut < 10) {
$idmax = "$kd" . "0" . $urut;
} else {
$idmax = "$kd" . $urut;
}
} else {
$idmax = "$kd" . "01";
}
$kode_admin = $idmax;

Answer 1

$model = Admin::find()->orderBy(['kode_admin DESC'])->all();
foreach($model as $m) {
$m->kode_admin = $this->createKode();
$m->save();
}
Admin is the model for tbadmin table, and createKode could be a function in your controller.
If your are creating a new Admin:
$model = new Admin();
$model->kode_admin = $this->createKode();
$model->save();

Answer 2

$model = AdminModelName::find()->orderBy('kode_admin DESC')->asArray()->all();
foreach($model as $m) {
$m->kode_admin = $this->createKode();
$m->save();
}

Answer 3

create model with Gii Tools
$model = \app\models\tbadmin::find()
->select()
->orderby(['kode_admin => SORT_DESC',])
->all();