We recently purchased a website from another company. The site is indexed well in all major engines and it ranks fairly well for terms that we want to be ranked for. The site has good link popularity with thousands of links pointed to important pages throughout the site. We are in the process of updating/changing the backend data structure and the entire tech platform. As a result, all of the urls will change. I know that we should put 301 redirects on the old urls to tell the spiders that the page has permanently moved, but does anyone know how this will impact link popularity? In other words, will the 301 redirect solve the problem of not losing link popularity. Thanks for the help!

There really shouldn't been too much of an impact on the link popularity--as long as you use 301s. Keep in mind, though, that if the content existed before and you remove the content from the site then the links might go away over time. Other sites linked to interior pages because of their content--so naturally the links would go away if the content doesn't exist anymore.

If at all possible, even if the backend changes, I would do everything you can to rewrite the URLs so that the majority of your URLs don't change.