First we have to identify the right source of the data to import. On the basis of the data source we have to identify the right tool to use. For streaming data we can either use Cloud Pub/Sub or Cloud Dataflow - if the data source is event-based and we do not require any processing, we can go for Cloud Pub/Sub.
If data is in batches in the form of file, we can use Cloud Storage to store this unstructured data in the form of objects. For this purpose we can use gsutil or Storage Transfer Service - depending on the source of data.