This website provides the best support for migration from Magento1 to Magento 2, Magento1 support has no longer available from 30 June 2020 that implies there will be no longer any patches available for Magento 1, if any risky security issue arises etc related, there are no new releases Magento 1 theme and other extensions, All superb new security features are coming in Magento 2, so its must to migrate from Magento 1 to Magento 2.
All product data will be migrated excluding website themes and third-party extensions. The migration charges start from 599 USD.

Website:- https://www.magentoonetomagentotwo.com/