Try:
$all_pms = new WP_Query( [
'post_type' => 'pms-subscription',
'post_status'=>'active',
'meta_query'=>[
'meta_key'=>'pms_subscription_plan_price',
'meta_value'=> '126', // string
'meta_compare' => '=', // or > or < or !=
]
]
);
https://developer.wordpress.org/reference/classes/wp_query/#custom-field-post-meta-parameters
Although ..re-reading your question I’m not sure what you’re exactly looking for..
With this query you’re searching posts of type pms-subscription
having post_status
=active and custom field with meta_key pms_subscription_plan_price
and meta_value equals ‘126’