I am trying to open PDF files but ID telle ms that I am missing a plug in or something stopping me from opening the files
You cannot open PDF files with InDesign. You can place PDF files into an InDesign document.
There are also third party software packages and plug-ins that with some degree of success or other attempt to convert PDF into “live” InDesign content. Note that since InDesign's imaging model only supports a subset of what could be in a PDF file and that PDF is a “final form file format” that does not contain context such as even the concepts of words, sentences, paragraphs, articles, etc., such “conversions” employ heuristics which may not be entirely successful.