Regex pattern URL rewrite

Question

I need to redirect our old urls like the following using the IIS 7.5 url rewrite tool:

http://www.mywebsite.com/mypage.htm

or

http://www.mywebsite.com/first+level/second+level/mypage.htm (urls can potentially be one or more levels deep)

Here are the transformations that would need to take place:

1. Change .htm to .aspx
2. Change "+" to "-" (if they exist)
3. Add "/Pages" just before the name of the page

So the final result would follow this format:

http://www.mywebsite.com/mypage.aspx

http://www.mywebsite.com/first-level/second-level/Pages/mypage.aspx

Can anyone please help me with the regex to use?

Thanks