Honestly, I can't help you with that. There must be hundreds of files on your server that *could* have been infected. There were multiple exploits in older modules and components for Joomla. You'll have to compare each and everyone with the default ones or open them to see if they're infected.
If I were you (and believe me, I've been there and I know how hard it is to throw your work away), I'd remove all files from my server and start with clean installs with the most recent versions.
Make a sitebackup first, though, maybe your host is able to determine whcih files are infected.