How can I obtain the partyId when updating inventory?

I want to update inventory using submitInventoryUpdate(https://developer-docs.amazon.com/sp-api/docs/vendor-direct-fulfillment-inventory-api-v1-reference#partyidentification). How can I get the partyId in my vendor account?
<img width="1401" alt="image" src="https://github.com/clousale/amazon-sp-api-javascript/assets/80157042/4ddbbc46-5da3-4331-b503-c83fe388d007">
