Moving items from one Bucket to another

Hi All,

I have the below scenario, if you can help me out

I have Bucket A , under which I have 100 items,

Later Business decides that they need 2 more Sub Buckets B and C to be created under A, as below

Bucket A

-----------------Sub Bucket B

-----------------Sub Bucket C

In this case, system wont allow me creating bucket B and C in first place.

How can I achieve my scenario of creating these buckets and transferring Items / Initiatives created from Sub Bucket 1 to Sub Bucket 2

Thanks,
Steve