Moving from another Sage product, such as Sage 50/100/200/1000, means you would need a new implementation. It would be classed as a new ERP system.
All Sage solutions, including some of the older products, are quite different in how they are structured and deployed. Sage X3 is similar in this respect but we have had extensive experience with assisting customers with the move to Sage X3, irrespective of their incumbent system.
For more information, download our ‘It’s time to upgrade from Sage 500/1000 guide‘.