Building a new server from a Dell Precision 490

Good morning,

My old Unraid server has finally reached the point where it needs to be retired. I really don't want to build a new server. But instead maybe I can use an oldr computer as I did before (that server lasted nearly 8 years!). I recently upgraded to a nice new Dell 8940 and my old Dell Precision 490 is now available to use as a UnRaid server. 

Here's some relevant specs from the Dell 490:

        CPU
            Intel Xeon DP 5060
            Dempsey 65nm Technology
        RAM
            8.00GB FB-DDR2 @ 332MHz (5-5-5-15)
        Motherboard
            Dell Inc. 0F9382 (Microprocessor)
        Graphics
            ASUS VH242H (1920x1080@60Hz)
            VE248 (1920x1080@60Hz)
            256MB ATI FireGL V7200 (Microsoft Corporation - WDDM) (ATI)
            ATI FireGL V7200 Secondary (Microsoft Corporation - WDDM) (ATI)
            CrossFire Disabled

I have (2) 4tb drives and (1) 1tb drive that contain the data from my old server which was runnng ver 5.05 basic

My questions are:

1.)  Using this Dell Precision 490, which version of UnRaid can I install?

2.) Can I just drop my old hards disk(s) into this new server and recover the data from them?

Thanks