We have received a ftp dump of all the files from a Wiki running version 1.24.2, and are trying to get it running on a new server. However, we haven’t had much luck getting it to work if we move the files into a modern version of MediaWiki. Do we need to get these files running on an old version of MediaWiki before upgrading, or is it possible to upgrade these files to make them functional on a current MediaWiki release without installing 1.24.2 first?
Topic on Project:Support desk
By "we move the files into a modern version of MediaWiki", do you mean all the files and directories or just the images/uploads directory and LocalSettings.php file?
See Manual:Upgrading#Using a tarball package.
You shouldn't "need to get these files running on an old version of MediaWiki before upgrading". Also did you receive the database backup too, because that is the most significant part of the old Wiki, comprising of almost all of the Wiki content.