I can read the Win 7 drive, so how do I run that Windows drive?
Do I access it through the Linux Mint, or ???
It is the original drive from this laptop that I picked up on the BC Auction.
I replaced that original drive with an SSD that I had Mint 19 on, then installed the Win HDD into the Extrabay. There are some Ham Radio programs written for Windows that haven't been ported to Linux.

Run update-grub and see if Win7 appears in the grub menu.

ThinkPad-T430:~$ sudo update-grub
[sudo] password for xxxx:
Sourcing file `/etc/default/grub'
Sourcing file `/etc/default/grub.d/50_linuxmint.cfg'
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-4.15.0-47-generic
Found initrd image: /boot/initrd.img-4.15.0-47-generic
Found linux image: /boot/vmlinuz-4.15.0-46-generic
Found initrd image: /boot/initrd.img-4.15.0-46-generic
Found linux image: /boot/vmlinuz-4.15.0-20-generic
Found initrd image: /boot/initrd.img-4.15.0-20-generic
Found memtest86+ image: /boot/memtest86+.elf
Found memtest86+ image: /boot/memtest86+.bin
Found Windows 7 on /dev/sdb1
done

now it no longer sees the win 7 drive in grub

udo update-grub
[sudo] password for dirkandjoh:
Sourcing file `/etc/default/grub'
Sourcing file `/etc/default/grub.d/50_linuxmint.cfg'
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-4.15.0-48-generic
Found initrd image: /boot/initrd.img-4.15.0-48-generic
Found linux image: /boot/vmlinuz-4.15.0-47-generic
Found initrd image: /boot/initrd.img-4.15.0-47-generic
Found linux image: /boot/vmlinuz-4.15.0-46-generic
Found initrd image: /boot/initrd.img-4.15.0-46-generic
Found linux image: /boot/vmlinuz-4.15.0-20-generic
Found initrd image: /boot/initrd.img-4.15.0-20-generic
Found memtest86+ image: /boot/memtest86+.elf
Found memtest86+ image: /boot/memtest86+.bin
done

Your earlier post shows a windows entry in the update-grub so what happened? Have you been able to boot windows since then? Did it not work/boot at all? What changed? Did you install windows 7 on this drive recently or was it on the drive and you changed it's location? Your post has too little information for anyone to help.

check your connection to that drive..
not a permanent fix, but you can see if supergrub2 burned to a usb stick you do not need at the moment, use that to boot from and have it search your hdds to see if it will pick it up and boot into it to see if windows still works. then you can go from there.

I can see the drive in COMPUTER, but can't mount it.

or what do you mean you cannot mount the drive, what have you tried?