You have that data backed up elsewhere in addition to on the hard drive, right? If not, that's a mistake and a big problem. You should always, ALWAYS have any important data backed up to more than one location, like flash drive, optical disks (CD, DVD, BD), another internal or external drive, your primary drive, cloud storage, etc., because it's NEVER a question of whether a drive will fail or not, it's only EVER a question of WHEN. New drives fail all the time and some old drives keep on chugging even after years and years. You can't trust important data to be in only one location without expecting that something like this might happen, because, it always does.
Does the drive show up in the BIOS or in disk management?
https://www.lifewire.com/disk-management-2625863
Have you tried a different USB port and/or USB cable?
What are your full hardware specs?