Hard Drives Options

If I buy a My Cloud EX2 Ultra 0TB 2-Bay External Network Storage from Best Buy, could I use my own drives that I already have to be used at the storage, or do I have to buy certain hard drives from Western Digital that only work with the My Cloud products?

@PCBOSS
You did not say what HD’s you have, but, I suggest this.

https://www.wdc.com/products/internal-storage/wd-red.html#!

You may want to post in the correct sub-forum too.
http://community.wd.com/c/network-attached-storage