You can find keywords for your SEO strategy through a couple of different methods. There are online keyword tools like SEMRush, Ahrefs, or even Google Ad words. These tools provide multiple data points that help you make wise decisions in selecting your keywords. You can leverage Google Search Console to get a basic understanding of what keywords you currently get exposure for.
SEO is more than just picking keywords though. It is recommended that you have someone on your team that truly understands how good SEO is implemented and how truly great sites and content are created.