5 year old joomla site recreated to new functional one in latest version

I have an old joomla site which was custom made 5+ years ago with a specific order function system and obviously this doesn't work anymore with new versions of joomla. So what I need is for someone to take the files, check the old joomla site and then modify/update/create/whatever in the latest joomla version so that everything works properly! You will work on your own server during the project and show me the progress and I'll also test on your server and then once everything is finished you will move the entire thing to my domain whereby we will do final testings to ensure that everything works fine whereby the job will be finished and paid for.