Welcome to Shopify Community.
We’re LitExtension - the world-leading shopping cart migration expert. Our company has had the honor to perform 150,000+ shopping cart migration projects for over 50,000 customers worldwide.
Regarding your question, don’t worry! LitExtension can help you SEO performance because currently, we provide “Create the 301 redirects options” when moving to Shopify. This option will help you avoid 404 errors when customers accessed the old URLs, which will maintain customer experience and also pass all the power scores to your new URL (maintain SEO ranking).