Change array type number to letters and numbers [on hold]

Change array type number to letters and numbers [on hold]

Need change Array 'type' => 'number' to letters and numbers
$this->settings = array(
array(
'name' => __( 'Heureka API', 'heureka-overeno' ),
'type' => 'title',
'id' => 'apiKey_nove'
),
array(
'name' => __( 'API k¾úè', 'heureka-overeno' ),
'desc' => __( "Nastavte si svoj API k¾úè (Nesmie
zaèína nulou).", 'heureka-overeno' ),
'id' => 'apiKey',
'type' => 'number',
),
array( 'type' => 'sectionend', 'id' => 'apiKey_nove' ),
);
APIkey looks like 31ce06d6a618f342618a1d7bme9413i6 and limits looks like
(^[0-9abcdef]{32}$)
Thank you for your help.