cannot send user_meta

Hello,

I am trying to send the usermeta values from a site to another, the user in created, and everything is fine, but the usermeta value is not getting stored.

$s=array(
		"billing_phone"=> "00000000000",
		"billing_address_1"=> "adress",
		"billing_postcode"=> "0000000"
		);
	$data=array(
		"username"=> "username-tests",
		"user_login"=> "username-tests",
		"first_name"=> "username",
		"last_name"=> "tests",
		"email"=> "[email protected]",
		"password"=> '000000',
		'AUTH_KEY' => 'the-key',
		'user_meta'=> $s,
	);

this is a sample code that I am using. I also tried using json_encode($s) but it is not working.
I am new to JSON and REST API, so I am pretty sure I am getting something basic wrong.

Please let me know how the metadata should be sent, possibly with a sample code in php.
Thanks.