Hi @leanne-oleary
Version 5 is another name for ACF PRO and version 4 is the free version. This page should give you more idea about it: https://www.advancedcustomfields.com/resources/acf-pro/. If you want to use ACF version 5, please check this page out: http://www.advancedcustomfields.com/pro.
Thanks 🙂