It’s completely impossible to tell because it depends on the hardware and the distance (latency) between the 2 locations.
If you want to migrate with zero downtime, it’s possible but you’ll have extra steps. I would take a full backup and restore it in the new location on a new node, then add this node in the replica set (repeat for each RS). Continue to add more nodes in your config until you can start removing nodes in the old location. Check that all the nodes are up-to-date.
You can play with priority settings to make sure the primary stays on the desired side until you are ready to “move”.
Cheers,
Maxime.