Query re redirect old site to a new wordpress

Hi

I am about to replace an old website created and uploaded through a Mac with a wordpress website. I am also changing the hosting from Freeola to Dreamhost. The old and new webiste are both using the same domain name but will have different page names. Therefore my concern is what is the easiest way to redirect someone who clicks on a page on the old site say through a google search that does not exist to a new page.

Thanks

Alex