You can put your DocumentRoot folder anywhere you want. Just because the default happens to be "/var/www", that doesn't mean you can't change your httpd.conf to point back to "/srv/www" (or whatever you prefer).
Furthermore, you can change each different project (for example, Drupal or MediaWiki) to point to their own physical directories, via "Alias" or "VirtualHost" sections in your http.conf file.
Q: Are your old directories still there?
Q: If not, do you have backups?
In either case, you should easily be able to use your old projects and old files with your new system (hopefully, with few - if any - source changes!)
'Hope that helps .. PSM