iPad Mini 6 file USB C transfer from SD to hard disk

The iOS/iPadOS native copy feature does not readily support bulk transfer between external storage media devices.

As you have spotted, using native capabilities, you will potentially need to engage in a two stage process to first copy data (photos) to your iPad - and then perform a second copy from the iPad to your external archive (your hard drive).

The are better third-party file manager Apps that can perform both bulk direct transfer between external storage devices - and support in-place editing.

Perhaps consider Stratopherix FileBrowser - Document Manager, or its “pro version” FileBrowser Professional:

https://apps.apple.com/app/filebrowser-document-manager/id364738545

https://apps.apple.com/app/filebrowser-professional/id854618029

You might review the extensive online Manual and help files to determine suitability for your needs.

https://www.stratospherix.com/products/filebrowserprofessional/filebrowser-professional-user-guide.php

You will also need a suitable hub. Speaking of personal experience, the Kingston Nucleum has proven itself to be particularly flexible for connection of USB storage devices - featuring twin USB3.1 Type-A, downstream USB-C and SD/microSD card slots, HDMI, plus a power pass-through USB-C port that can accept +45W from a suitable USB power source.

Otherwise, perhaps consider Kingston, Anker, Hyperdrive and Satechi - although there are many others from which to choose. A Google Search for USB-C Hubs compatible with iPad will find a number of articles and recommendations. 

You may find this support page to be helpful with connecting external storage to your iPad:

Connect external storage devices to iPad - Apple Support

You should note that you will almost certainly need to connect your iPad Power Adapter or a portable PowerBank while using external storage, in particular when using an HDD drive. Also be aware that storage media and drives must be formatted as FAT, FAT32 or exFAT (FAT64), with a single data partition.

The iPad Mini 6, equipped with a USB-C port, should be able to handle this kind of file transfer operation. Here's what you'd need to do:

1. Purchase a USB-C hub that includes both an SD card slot and a USB port. This will allow you to connect your SD card reader and LaCie hard drive simultaneously to your iPad.

2. Transfer the files from the SD card to the iPad using the Files app. The SD card should appear in the Files app once it's connected through the hub.

3. Next, connect your LaCie hard drive to the iPad using the USB port on the hub. Your hard drive should also show up in the Files app.

4. Then, copy the files from the iPad to the hard drive. It may not be a direct transfer from the SD card to the hard drive, but this process should work without requiring too much storage space on the iPad.

In terms of an app, the native Files app on the iPad should handle this without issue. No extra app required. This solution, though, relies on your iPad having enough temporary storage space to accommodate the largest file you'll need to transfer.

Here are some resources to assist you:

1. How to use external storage with an iPhone or iPad

2. How to manage files on your iPad

3. How to use the Files app