REST api : inventory/get-product-salable-quantity/{sku}/{stockId} – where to obtain sourceId… or is it actually {sourceId}

the API documentation says the 2nd parameter iis stockId
https://magento.redoc.ly/2.4.5-admin/tag/inventoryget-product-salable-quantityskustockId

This tutorial says it’s sourceId
https://developer.adobe.com/commerce/webapi/rest/tutorials/inventory/create-cart-add-products/

IF it’s sourceId, where do I obtain sourceIds ??

Seems like if anything would return a sourceId, it would be
https://magento.redoc.ly/2.4.5-admin/tag/inventorysources#operation/PostV1InventorySources

which seems to return everything but an id.

{ "items": [ { "source_code": "default", "name": "Default Source", "enabled": true, "description": "Default Source", "latitude": 0, "longitude": 0, "country_id": "US", "postcode": "00000", "use_default_carrier_config": true, "carrier_links": [], "extension_attributes": { "is_pickup_location_active": false, "frontend_name": "" } } ], "search_criteria": { "filter_groups": [] }, "total_count": 1 } 

This is so painful

https://magento.redoc.ly/2.4.5-admin/tag/inventorystocks
Why is sku not a field that I can use to search??

How do I get stock qty for a sku for each of my warehouses?

With Magento V!, this was /multiwhse/id/sku1,sku2,sku3…