how can I convert Facebook page to app. is it possible.?
I recommend searching for it on google. Ionic is not the easiest version. I even don’t know if it is possible with Ionic. But there are great solutions on the web with other technologies.
https://www.google.de/search?q="facebook+page"+to+"mobile+app"&oq="facebook+page"+to+"mobile+app"
Please use Google before posting any question here.
Did you consider reading the docs before or did you even try anything else before asking other People to do your work?
Maybe the Inappbrowser is what you are looking for.