sort GCP billing data by metadata tags

I'm a little confused in GCP with tags, labels and metadata and I do not find how to sort my billing informations by the metadata tags i set for every objects in the storage. I have added a metadata tagging process which gives the id of the account that uploads a file through signed url headers or through blobs uploads. Then I launch requests on the billing with big query. ...but I do not see my tags in the "labels" field of the exports How can I enable metadata tags sorting on billing exports ?