There is no term for this, at least in English. There are verbs referring to the process of conversion and, usually consecration/reconsecration, but no single noun encapsulating the concept.

An associated term would be spolia--objects removed from their original cultural context usually through conquest and displayed in or incorporated into another context--but the term does not normally apply to entire buildings, being used instead to refer to moveable objects.

I doubt this is the right place to post your question. I would recommend you head over to http://english.stackexchange.com/ they field these kinds of questions all the time and very often give very good answers.