Re: Remarketing Campaign
Not Google conversion code, but remarketing tag you need to add it to all your website pages.
check the next link for all information about remarketing tag and how to add it to your website:
I believe you should implement remarketing code on all the pages which will help you in creating custom combinations of users with relevant ad copies.
As far as conversion code is concerned, it has nothing to do with remarketing code but you should implement to track conversions on adwords.