How to migrate unfulfilled orders to a new fulfillment orders workflow?

[bcurtis]

I am trying to migrate a shop from the legacy fulfillment work flow to the new fulfillment orders work flow required by 3/31/2023.

I have created a fulfillment service via the REST api and set the fulfillment_orders_opt_in to true and provided a call-back url.

It appears that all Products need to be set under Inventory to fulfill from the new app via name.

New orders coming in are creating fulfillment Orders and I can pull them.

Existing orders that were created under 2022-04 after the last polling do not create fullfilment orders.

How do l make existing unfulfilled orders create assigned fulfillment orders for the new fulfillment service app?

Also, when I look at the Order resource line_items for existing unfulfilled orders and new ones the fullfillment_order_id of the line_items = 0.

Would greatly appreciate guidance from anyone.

[rminocha]

Were you able to find help on this? We are looking to solve the same problem.