What will be the preferred way to migrate pinned files from cluster A to cluster B? can it be done externally without having internal access to cluster A

B is a managed cluster by Infura, and A is a cluster that I want to copy the files from.

Just pin them on the cluster B.
IPFS cluster only manages the pins but files exchanges and discovery are done with IPFS.
So the cluster B will download from the cluster A, maybe other from B while they download or others random IPFS node having your files (it’s the magic of IPFS this will get done depending of speed and availability).

Thanks, so I guess I can iterate on all the pinned files in my cluster and pin them on another cluster.