The correct option is AzCopy.

AzCopy is a command line tool that is designed for large scale blob transfers. It can be scripted for automated workflows with minimal operator intervention and it supports resumable transfers so a multi‑terabyte copy across many containers can continue after interruptions without manual restart. It also uses parallelism and other optimizations to achieve high throughput when moving data between storage accounts.

Azure Data Factory can perform copy activities and is useful for orchestrated ETL and scheduled jobs but it requires more configuration and operational overhead. It is not the simplest, most direct tool for a straightforward, resumable bulk blob copy.

Azure Storage Explorer is a graphical tool that is convenient for exploring storage and doing manual file or blob operations. It is not intended for fully automated, unattended bulk transfers across dozens of containers and it lacks the same resumable, high performance capabilities that AzCopy provides.

.NET Storage Client Library gives full programmatic control and you could implement an automated, resumable transfer yourself. That approach requires custom development and effort to handle resume logic and parallel performance. It is therefore less appropriate when an off the shelf, scriptable tool like AzCopy already meets the requirements.

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