what should i do with .do extension ?

I have a site that had .html extension than for two months its extensions were changed to .do extension...now some of keywords are ranked in .html extensions and some in .do whats the possible solution to sort out this problems?
dynamic pages cannot be converted into .html extensions so what the possible solution
what i have suggested
Keep the .do extensions and redirecting .html extensions...is this right solution ?
or should i make site with partially .html extensions and partially .do extensions
Suggestions needed

.html extension is most Search Engine Friendly one. I prefer you to redirect .do to .html extension OR make ONLY 1 extension site. (HTML)

You will get more boost in SERP with .html extension so to me you dhould go with .html...

SionAndes said:

.html extension is most Search Engine Friendly one. I prefer you to redirect .do to .html extension OR make ONLY 1 extension site. (HTML)

Click to expand...

I agree but problem lies in some pages that has to have .do extensions like cart and dynamic pages(compulsion)..now how do i deal with that ? should i keep them partially html and partially .do extension?

The SEO said:

You will get more boost in SERP with .html extension so to me you dhould go with .html...

Click to expand...

you mean to say partially html and partially .do extension ? since it almost a compulsion to have .do extension in few dynamic pages