That could be a lot. I use sites like [wordtracker.com...] to find out how much this would be but its in the millions for sure. If you want to go to the top on the google regular search results with shopping malls you are looking at a serious SEO job :-)
Adwords is probably a faster way to get visitors (albeit more expensive)
shopping malls produces 1.5 clicks/day
whereas its exact clone
[shopping malls] produces 55 clicks/day
how is this possible? this is against common sense ...
eg. online shopping malls
shopping malls of america
and etc.
will also give my ad if i choose
shopping malls
but if i choose [shopping malls],then it will be shown when someone searches exactly
shopping malls
and nothing else .....
This is assuming you have all 3 flavours in your account, if you just went broad and nothing else then you would end up with probably a much higher estimate, but would end up getting your ad turned off because of relevancy, a keyword like you suggest will always struggle as a broad match.
Hope that helps.