use FacebookAds\Object\AdCreative;

$creative = new AdCreative(<CREATIVE_ID>);
$creative->getPreviews(array(), array(
  AdPreviewFields::AD_FORMAT => AdPreviewAdFormatValues::DESKTOP_FEED_STANDARD,
));

from facebookads.adobjects.adcreative import AdCreative
from facebookads.adobjects.adpreview import AdPreview

creative = AdCreative(<CREATIVE_ID>)
params = {
    'ad_format': AdPreview.AdFormat.desktop_feed_standard,
}
ad_preview = creative.get_previews(params=params)
print(ad_preview)

APINodeList<AdPreview> adPreviews = new AdCreative(<CREATIVE_ID>, context).getPreviews()
  .setAdFormat(AdPreview.EnumAdFormat.VALUE_DESKTOP_FEED_STANDARD)
  .execute();

curl -G \
  -d 'ad_format=DESKTOP_FEED_STANDARD' \
  -d 'access_token=<ACCESS_TOKEN>' \
  https://graph.facebook.com/v2.11/<CREATIVE_ID>/previews

GET /v21.0/<CREATIVE_ID>/previews?ad_format=DESKTOP_FEED_STANDARD&product_item_ids=%5B%22%3CPRODUCT_ITEM_ID%3E%22%5D HTTP/1.1
Host: graph.facebook.com

/* PHP SDK v5.0.0 */
/* make the API call */
try {
  // Returns a `Facebook\FacebookResponse` object
  $response = $fb->get(
    '/<CREATIVE_ID>/previews?ad_format=DESKTOP_FEED_STANDARD&product_item_ids=%5B%22%3CPRODUCT_ITEM_ID%3E%22%5D',
    '{access-token}'
  );
} catch(Facebook\Exceptions\FacebookResponseException $e) {
  echo 'Graph returned an error: ' . $e->getMessage();
  exit;
} catch(Facebook\Exceptions\FacebookSDKException $e) {
  echo 'Facebook SDK returned an error: ' . $e->getMessage();
  exit;
}
$graphNode = $response->getGraphNode();
/* handle the result */

/* make the API call */
FB.api(
    "/<CREATIVE_ID>/previews",
    {
        "ad_format": "DESKTOP_FEED_STANDARD",
        "product_item_ids": "[\"<PRODUCT_ITEM_ID>\"]"
    },
    function (response) {
      if (response && !response.error) {
        /* handle the result */
      }
    }
);

Bundle params = new Bundle();
params.putString("ad_format", "DESKTOP_FEED_STANDARD");
params.putString("product_item_ids", "[\"<PRODUCT_ITEM_ID>\"]");
/* make the API call */
new GraphRequest(
    AccessToken.getCurrentAccessToken(),
    "/<CREATIVE_ID>/previews",
    params,
    HttpMethod.GET,
    new GraphRequest.Callback() {
        public void onCompleted(GraphResponse response) {
            /* handle the result */
        }
    }
).executeAsync();

NSDictionary *params = @{
  @"ad_format": @"DESKTOP_FEED_STANDARD",
  @"product_item_ids": @"[\"<PRODUCT_ITEM_ID>\"]",
};
/* make the API call */
FBSDKGraphRequest *request = [[FBSDKGraphRequest alloc]
                               initWithGraphPath:@"/<CREATIVE_ID>/previews"
                                      parameters:params
                                      HTTPMethod:@"GET"];
[request startWithCompletionHandler:^(FBSDKGraphRequestConnection *connection,
                                      id result,
                                      NSError *error) {
    // Handle the result
}];

curl -X GET -G \
  -d 'ad_format="DESKTOP_FEED_STANDARD"' \
  -d 'product_item_ids=[
       "<PRODUCT_ITEM_ID>"
     ]' \
  -d 'access_token=<ACCESS_TOKEN>' \
  https://graph.facebook.com/v21.0/<CREATIVE_ID>/previews