How to deal with internal links in blog while developing new site in WordPress?

For the best SEO results (and the best likelihood that human visitors will get where they’re trying to go), you should do two things:

  1. Update the URLs in the database. Usually this is best left until the end; once you have all the content moved onto the dev/staging site and you’re about ready to go live, you can run a script to search and replace the old URLs with the new ones.

  2. Add 301 redirects for everything. It looks like this will be a fairly simple step based on the structure you specified; you can simply redirect everything in the resources folder to (site)(whatever was after /resources/ in the old URL). This way, visitors who click an outdated link will still get to the right page, and the 301s also signal to search engines that you’ve permanently moved the content.