Don't do anything rash, yet.
First read the following on EFI.
These instructions are for Ubuntu, but the same steps would apply to Mint.
The critical one is getting a Mint that installs using EFI.
It sounds like your Mint is trying to use the BIOS interface.
Linux bypasses BIOS for many drive accesses, but still needs a few basic BIOS operations to boot. If the machine is in EFI mode, then it is using a new different boot interface.
Your Mint could be totally confused, especially if it bypasses BIOS for some drive accesses,
and tries a BIOS valid method which is not EFI compatible. The possibilities for screw-up are endless. The Mint needs to be in EFI mode too.
Linux source code has hundreds of options that are selected before compiling. Using a pre-compiled kernel like Mint means you are limited to which of those options were selected.
With Slackware, you install a HUGE kernel and use that, or can compile a Linux kernel customized for your hardware by you selecting options. There is a whole section of kernel options on what filesystems are in the kernel, and what disk partition schemes the kernel understands. Most machines in the world used the PC disk partition, with work-arounds because it really was designed for drives less than a few GB in size, and it is possible some distributions have assumed that case too much, and may not even have provided the kernel options to read other type partition tables.
That machine has EFI and BIOS, but if the drive is partitioned using GPT and requires using EFI to read the partition table, then Mint using BIOS will never find valid partition tables on the drives.
There is also the possibility of it using an EFI partition. Right now, I don't know if that is another name for GPT, or another partitioning format. Ubuntu can handle it, and
the Mint you are trying seems to not recognize it (whatever it is).
1. Can go back to using BIOS.
Will have to switch the machine back to BIOS mode (not EFI).
Then will have to repartition the drives using a partitioning tool.
A 1T byte is large enough that you will have to look closely what the limitations are for partitioning. There are alternatives for partitioning that use more capable partition formats than the PC does, but they might not be supported by Mint either.
One of those is GPT, which is what your drive is probably using for the partition table.
2. Find a Mint for EFI, or switch to the Ubuntu EFI installer.
Then can keep the drive partitioned as it is.
3. There should be a way to use GPT partition tables using BIOS and a Mint that installs using BIOS, but that is past the point I feel comfortable making recommendations.
It would require a Mint that understands GPT, and is in GPT partition table mode.
If it installed using BIOS, then would have to switch the machine to BIOS mode (not EFI).
The boot would then be by BIOS, using GPT partition tables.
After the boot, Linux would bypass BIOS for most accesses, and if it has been compiled into the kernel, it can understand GPT partition tables (among many others). The question here would be, is the Mint distribution compiled with kernel handling for GPT partition tables.
4. The HUGE kernels in a distribution like Slackware, have just about everything possible compiled into that kernel. They also provide pre-compiled kernels that are not so huge. Ubuntu may also have kernels like that.
Mint may be easy and simple to install, but sometimes you get past the capability of the easy and simple distribution and need to use one of the full-featured ones.
5. Get GPARTED and investigate what partition type is on that drive.
Follow GPARTED instructions for this. Do not change anything, just find out what it is.
What is on the drive is probably best for using that drive, but the Mint (or Ubuntu) must
know and be capable of reading that partition format. This will tell you what drive partition type to compare to the Mint install limitations.