Moving My Html/php Website To Wordpress, How To Do It Without Losing My Rankings In G

Hi there,

I have a website that I would like to transfer from HTML to wordpress, in order to be able to write more often and more efficiently.
However, most of my webpages on the site end with *.php, and if I move the page to wordpress, the pages will not end with *.php, and my rankings in google will probably suffer.
Are there any way around this? I thought about moving my template to wordpress, then just add these pages that I already have (it is not that many) over to wordpress manually, with the *.php endings.

For your information, I only want to add wordpress to the sub-categories cricket picks and blog, the rest of the site could be HTML for all I care.
Anyway to add the same wordpress install to two different sub-categories?

if you know the structure of the existing html url converting to a wordpress url you could use htaccess to do a 301 redirect telling google the page has been moved permanently. this should update google with the new url and also anyone who has the old article bookmarked will still be able to access the page.