Hi,
I'm struggling to get the correct syntax to update the value of a lookup column of a file in a document library. I've looked at this post (and the article that it points to):
https://powerusers.microsoft.com/t5/Building-Flows/Need-correct-syntax-to-update-lookup-column-property-using-HTTP/m-p/529092#M68119
However, there's still quite a difference between the syntax needed here and that for the 'Send an HTTP request to SharePoint' action in Power Automate. I've tried a syntax which just adds the string 'Id' to the end of the lookup column name and sets it through POST request:

However, it throws this error:

Would someone please be able to help me out with this?
Thanks