When using ads manager, you can preview ad. There is also a hyperlink which goes View post permalink with comments. Is there any way to get that link using API
First you must get the creative that's targeted by the ad.
$ad = new Ad($ad_id);
$ad->read(array(
AdFields::CREATIVE,
));
Then get the info from the creative.
$creative = new AdCreative($ad->creative['id']);
$creative->read(array(
AdCreativeFields::EFFECTIVE_OBJECT_STORY_ID,
));
Then $creative->effective_object_story_id
will contain an ID that would look like xxxxxxxxxxxxx_yyyyyyyyyyyyy, where x is the ID of the page, and y is the id of the post/video/etc.
If you just go to https://facebook.com/xxxxxxxxxxxxx_yyyyyyyyyyyyy it should redirect you to the correct post
Hope this helps someone.