SEO-Safe Magento to Shopify Migration

I’m moving my current Magento site, which sells my jewelry designs, over to Shopify and I need the transition to be invisible to Google. Every existing URL must either remain exactly the same or be mapped with a flawless 301 redirect so rankings and indexed pages stay intact... (Budget: $250 - $750 USD, Jobs: Content Management System (CMS), Google Analytics, HTML, Magento, SEO, Shopify, Website Design, Website Development, Website Optimization, Website Testing)