Ok, I understand.
System sizing aspects include capacity, performance, parallelism, as well as constraints such as budget, space, power and cooling, and enhancements such as support levels and software licensing. This topic is probably too complex and commercially sensitive to cover on our forums.
At a broad stroke, a single HA pair of FAS9000 systems will likely meet your requirements, but without detailed analysis of your environment, we couldn't say that is the correct choice for you.
Your leasing reseller should be able to work with you to identify your sizing requirements for a replacement system.
Please use this form if you would like to contact our sales engineering team for your region - https://www.netapp.com/us/forms/sales-contact.aspx