I assume you have no backup of these files, or else you wouldn't be posting this.
As far as I know, there is no easy way to get the files back, and perhaps no guaranteed way at all. The actual bits on the disk may still be present, but they are likely not associated with their filenames anymore, so it is very hard to find them, even with Unix-level tricks. If I'm wrong, I'll be glad for your sake.
The less you use the disk in question, the more likely it is that the data is still on the disk and not overwritten. Any use of the disk can create files that overwrite what is now considered freespace, which might be where your files were stored. If you have lost data so valuable that it is worth hundreds or thousands of dollars, you can hire a data recovery service, which really does scan for bits of files and the pointers to them and can get back data you otherwise would have lost. But it is expensive.