I'm presuming that's meant to be 1.4TB of data. The drive has been converted to GPT & that's what has rendered your data inaccessible. You might be able to revert to MBR & recover your data but there's no guarantee.
First step:
DO NOT WRITE TO THE DISK!!!
Second step: download a program such as
https://www.easeus.com/partition-recovery/ to determine if your partition can be recovered. I don't know if there's free software that can recover it but at least the trial version will show you what's likely.
Use Solution 2 listed here:
https://www.easeus.com/data-recovery...onversion.html