SEO for React PWA and database

We have developed an Ionic React single page app with a large database and want to develop a way for search engines to search millions of business profiles and posting within the app. We will provide further details to a developer that we feel is qualified and negotiate the price.

To update this description of our needs note that our app is developed to promote other businesses locally. Our database currently contains over a million business listing that are attached to business categories and keywords, some have web links. We want to have the search engines find and post these listings by users searching location. Our success is in helping get their business found in their local community.

To further update... We don't believe that standard SEO functions will be adequate for this project as a a React SPA app is not searched by crawlers in the traditional methods. We need the data from our database presented for crawling. The successful freelancer should give us some idea how they may achieve this as the SPA will not render all the data from our database based on standard SEO programming.