Can't add drive without deleting data

So I just unpacked this anchor and it won’t let me add a new drive without deleting all the existing data.

I had a desktop with three bays and used a 3TB and a 1.5TB for storage. When I bought the EX4100, I bought a 4TB and I was hoping to simply add the 3TB and the 1.5TB with it. It sees the drives but I can’t access the data. And when I try all the RAID options, it wants to format all the drives before it continues!

Is this no possible???

No matter what I do, this piece of garbage keeps telling me my data will be deleted.

I’ve read there is an option to “migrate” the data but I can’t find that anywhere. I’d really appreciate some help here or at least be told this isn’t possible so I can throw this ■■■■ thing in the trash.