First step: do not attempt to run CHKDSK or scandisk or any other Windows feature. Those only break the drive further.
Best case scenario: there is a possibility that you can recover the data, or most of it, for free. Depends on how dead the drive is at the moment. If the disks still spin, there is a possibility.
Last time this happened to me, which was ages ago, I used “PC Inspector File Recovery” (freeware), which slowly but surely retrieved all the data from the disk. It’s still available at http://www.pcinspector.de/FileRecovery/instructions.htm?po=2&language=1 but it looks like it may not be very up-to-date (at least the installer still runs on Windows 10).
They also claim that it doesn’t work for mechanical failures, but that’s not my experience.
There are other, similar, programs available. Some free, some paid. At https://www.softwarehow.com/free-data-recovery-tools/ some of these are mixed in with ordinary file recovery tools. A paid alternative is available at https://www.easeus.com/
This works best if you keep the drive connected using SATA, not in a USB enclosure. Connect a new drive with 2TB of space to copy your stuff over.
If the data is essential to you, and you don’t want to risk making the problem worse, you may want to go straight to a paid data recovery service though.