Very Slow Transfer Speeds

Hi, I have just purchased a 12Tb WD MyBook Duo. I am copying files from an alternative external harddrive onto the MyBook Duo, but I am experiencing very slow transfer speeds (varying between 1-10Mb/s). I had understood USB3 was capable of transfer speeds of several hundreds of Mb/s. Is anyone able to help me understand why my transfer speeds are so slow?

I am using a Windows 10 laptop with USB 3, the MyBook Duo is formatted to NTFS and is connected to the laptop via a USB-C to USB-A cable. The harddrive I am copying from has an exFAT File System connected via USB-A to USB-A.

Is anyone able to help me understand why my transfer speeds are so slow?