converting from old Freenas version to new

I have a server with dual drives that has been running for 6 years and we are starting to have issues with connecting to it. I wanted to just update everything with new hardware and newest version of software but
can I mount my old drive and recover data on new version and hardware or are their limits like has to be same motherboard and so on? What is my best choice to recover and then get to new hardware / software and transfer data ???