I think that I might have delete all files from /tmp. How can I get them back?
Now I don't know about these specific files, but any application putting files in /tmp should be aware of that the folder may be removed at any time. So if you're just worried about losing "software files" or similar just rebooting should be enough to bring any files used by applications.
Otherwise if you lost some data file I guess you should look for a recovery software, but then I'd also like to ask why you were saving important files in /tmp. :)