I don't know why you did not use Directadmin's functionality to migrate your users, and don't know why you did not specify it in your posts.
You can copy content of files:
/etc/virtual/domain.com/filter
/etc/virtual/domain.com/filter.conf
to any other domain, and it should work, and you should see filters in Directadmin web interface and Exim should read and respect it, unless you ruin file permissions.