Found a few keywords need advice

Hey thanks for looking just wanted to ask, i have found a few keywords o am interested in getting to the top of they range between 400,000 and 1.4 mill search results on google, mostly yahoo answers and wiki answers top the results, with 1 or 2 being topped by sites which are only pr 1 and have like 3k backlinks.
I know i need to find out how many times these keywords are searched by actual users, but right now am i on the right lines so far in terms of finding a niche to get to the top of? If not then any advice on it would be very much appreciated.
Thanks again!!

Have you got market Samurai? If not. Get it.
Have you got Traffic Travis? If not. Get it.

sounds like an awesome set of keywords

Do you want to know the real number of requeries of necessary keywords? In that for you can help services such as GKT or Semrush. Here's,an example, in semrush you can see not only the number of requests, but also see graph, showing trends for a current domain or keyword

make sure you check numbers on adword keyword tool with EXACT searches and not BROAD