You can use any file recovery software. PC Inspector File Recovery is free for example.
Mind you, every second your computer spends turned on means more data potentially overwritten and gone forever. If the folder was on the busy system drive (C, then you are not going to get it all back.
When a file is permanently deleted, the filesystem space it was using is marked as unallocated.
Data Carving utilities like PhotoRec http://www.cgsecurity.org/wiki/PhotoRec can explore the unallocated space for known file headers and recover lost files.