Inserting existing php files

I am in the process of switching to wp after running my site with a css / php combination, where the main content of each page was in it’s own seperate php file, with headers, navigation, footers etc.. also all in seperate php files.

I have modified the default wp theme to my liking and now would like, if possible, to find a way to insert the main content from my old pages into my wp database. As the main content from each page is already in their own php file is there a way to get a new wp page to reference those php files?

Thanks.