Pentaho spoon - how to call variables ( previous step and transformation properties parameters and pass as API URL params in REST client step

Question

First off I am new to spoon and ETL and I am trying to extract from an API data and create an ETL for it.

The problem is the API have parameters as follow: &from=2023-08-10&to=2023-08-15

one approach I was trying take is in the job and step before the transformation use 2 date variables with assigned values in the job/transformation to those variables

First step in transformation

I also assign values again in this first step to same variables

API + variables as params

then last pass it to a REST CLIENT (https://i.stack.imgur.com/wTEBl.png)

I also tried directly using the variables in the URL in generate rows or creating them in generate rows and constructing the REST CLIENT step that way

But in any case either the output of API is incorrect because the results is out of the variables range or in case using javascript the URL + variables show as string.

In the end what I am trying to do is assign the params in the ETL so I can LOOP or schedule to run for a large date range that is out of the API params and not sure if this is the correct approach