why is my wordpress Jquery-Ajax call not working?

You need to change the data that you are sending in the ajax request.
For ajax to work in WordPress you need to send the action variable in ajax post request.
Change

data: {package: package},

to

data: {action: 'ajaxAutopopulate',  package: package}

Also you can use the wordpress default function

wp_send_json( $response ) 

for encoding of data
and

 admin_url( 'admin-ajax.php' )

for the ajax file url.

If you have your js code in a separate file , you may need to use

wp_localize_script

to pass the value to the js file