Nolan has a portable hard drive that can't be seen with his Mac anymore. How can he get the data off it? Leo says this is a perfect example of why you need more than one backup of your data. You can't back up your data onto a hard drive and then delete it from your computer and think you have a backup. You don't. The best backup strategy is a 3-2-1 backup strategy. Three backups, on two different media, one off-site. That's the only way to be safe.
Leo thinks that Nolan's hard drive isn't bad, it's just the enclosure that has probably been damaged. If you can get a new enclosure and remove the drive, then you can get your data off the easy way. Leo recommends getting the NewerTek USB Universal Drive Adapter. It'll attach to your hard drive, power it, and then connect it to your computer. Then you can get the data off. Hopefully, the drive has "soft" errors, which you can get off with software. A good utility for that is called SPINRITE by GRC.
But if it's a hard failure, then there's a problem with the hard drive and you'll likely have to have someplace like DriveSavers get the data from you, and that can be expensive: like thousands of dollars.