Conversion metrics not appearing in response when requested


Currently, I’m trying to grab the following metrics for a list of promoted tweets:
However, in the response, these metrics aren’t even listed as having a value of 0. They just aren’t present.

In the parameters I’m specifying a segmentation type of PLATFORMS, granularity by DAY, and I give it a start and end time of the past 3 days. I’m using solely the metrics listed above right now and it still is missing in the response. Anything I’m doing wrong still in terms of what I’m supplying for params? Or is it related to the section I’m looking for these parameters for - that is, should I be asking for this at line_items, or campaigns?