Check checkbox of post expirator if post is set to specific category

Hi,

we would like to run the post expirator plugin only if the post category is set to a specific category.

I am currently looking at a piece of code which fires on the save post hook, but I would need to know where the checkbox value is typically stored in the mysql database for this to work.

could you help me with this please ?

I have currently this, but it won’t work so I need to alter it to look at the meta value created by the plugin

function expire( $post_id ) 

if (has_category('39',$post->ID))
{
    $( "#enable-expirationdate").prop('checked', true);
}
else
{
    $( "#enable-expirationdate").prop('checked', false);
}

add_action( 'save_post', 'expire' );