The migrating platform is not an easy job, It needs extraordinary understanding & technical knowledge. We need to set up proper redirects, copy meta titles, description etc so current Google rank must not affect. Kindly share website URL so that I can get an exact idea about the project scope of work and offer my best estimation.
Technically, I'm having strong experience in working on Magento & Shopify platforms. In last eight years, I worked on more than 300+ ecommerce stores. Happy to share references in detail proposal.
Anxiously waiting for your to moving forward from here.
Warm Regards,
Sugan Chand