I second @dtlow and also highly recommend that you consider using Tags to create your hierarchy.
My recommended reading on this topic: https://michaelhyatt.com/evernote-tags.html https://byrslf.co/using-evernote-the-right-way-ef61f530d1ad#.ow0hprchu
There are a few mind map software packages that have integrated with Evernote. http://lifehacker.com/mohiomap-creates-a-mind-map-to-browse-your-evernote-1508827115 https://appcenter.evernote.com/app/conceptdraw-mindmap/mac http://www.xmind.net/ http://noduslabs.com/cases/evernote-iphone-notes-text-network-graph/