While it would be possible to move a store from one portal to another, a few things have to happen.

1) You need to be licensed for the new portal.

2) You would need to have the store configured on the new portal.

Probably easiest would be then to somehow export/import the store items if there are a lot of them.

Otherwise, off to SQL Studio, and there are several tables that would need to be updated to move things over, including many with the PortalID, ModuleID, and so forth.