Passing a Parameter to mQuery Variable

Hi I have a query that retrieves data from an API in POST that looks like the below:

let
    Source = let
    Source = let
    Source = let
    Source = let
 url = "https://url.com",
    body = "{""id"": ""0001"", ""variables"":  {""variable"":  ""001""}               }",
    Source = Json.Document(Web.Contents(url,[
        Headers = [#"Authorization"="Basic XX", #"Content-Type"="application/json"],
        Content = Text.ToBinary(body)
    ]))
in
    Source

I am trying to replace the ""0001"" text in variable field using a parameter, lets call it "Var1". I've tried replacing ""001"" with "= Var1" and "Var1", but I am getting errors. Could anyone assist? The idea is to have the user supply the parameter so that they can get their report.

Thanks!