Please Help me how to get back my old file!

Hi everyone,

I starting using My Cloud EX4100 4 HDD with RAID 0 use until full (we call it Set-A)
and bought another 4 new HDD make as RAID 1 (we call it Set-B),
after few months later, want to find some old file, so i remove Set-B and put Set-A back in…

“This volume is roaming from another WD My Cloud EX4100 (not created on this sytem). Click OK to integrate it into your current WD My Cloud EX4100. If you do not integrate it, you risk losing data if your volume becomes degraded. Click Cancel to continue without integrating it.”

if i press OK, will i lose my file in Set-A ? because i’m sure if i switch RAID it will format my file…

anyone can advise me how to get back my old file?