Formatting was the wrong step, unfortunately. If it was a quick format, you should be able to recover the data in most cases. If it was a full format, you have a problem.
There are a sequence of steps that we usually take recovering unreadable data from a failed external drive. These are
1) Try a different USB cable and a different computer. Just in case it's a trivial problem.
2) If you have the experience, remove the drive from the external housing and attach it directly to the motherboard controllers. This rules out problems with the housing electronics.
3) Run a free utility such as EASEUS Partition Recovery (there are many) that can read data from a disk that has had its partition / format data corrupted.
4) Run a utility that scans a drive sector-by-sector and tries to rebuild files. These can take several days to run. They are usually free to scan, but about $100 to recover more than one file. Sorry, I can't provide a list of these utilities. I recently lost my list of favorite threads with good answers to questions like these, so I can't just send you to an existing answer.
All this assumes that the disk is not making loud noises, emitting smoke or sparks, or otherwise indicating that the problem is physical damage.