Suggestions for how to configure HDD as primary userdata in HC2

I’ve had an Odroid HC2 running as a home server on DietPi for years, with a small microSD for boot, and the userdata all on a 14TB HDD in the SATA dock. I have just moved homes, and unfortunately the microSD sticks out a little and suffered physical damage in the move rendering it useless. I have flashed DietPi to a new microSD and can mount the HDD and see all the files there, but there is no longer the option to transfer rootfs to the HDD (I’ve read THIS similar thread from earlier this year).

What is the suggested configuration for this case? When I mount the HDD and select it as dietpi_userdata location, the terabytes of files are only found at /mnt/hdd/mnt/dietpi_userdata and are not presented when accessing via Samba, and I presume software installed will all default to interacting with the /mnt/dietpi_userdata location as well. Is the /mnt/dietpi_userdata location (with empty default folders) actually now on the HDD or still the microSD? Can I just copy (symlink?) everything from /mnt/hdd/mnt/dietpi_userdata to /mnt/dietpi_userdata and proceed?

Guidance and suggestions appreciated

Usually that’s what we do, creating a symbolic link from /mnt/dietpi_userdata to new location on HDD