Migration from Manage Purchasing Document Approval task in FSM to BPM

Summary:

Business is currently using the FSM approval for Purchasing approvals. Due to some new requirements which will require configuration of some custom approval rules depending on DFFs and other rules that can't be achieved through FSM., business needs to move to BPM while retaining most of the existing rules functioning. When we look at the BPM DocumentApproval, we can see that the current approval rules are correspondingly created in BPM, we have a few questions on this:

1. Are there any steps that we can be performed so that everything in FSM gets transformed to BPM?
2. Do we need to disable the existing configuration in FMS and create rules in BPM from scratch?