What is the best way to use dataLayer custom variable in Google tag manager for sales tracking in google ads

My gtm script is already setup. and dataLayer push is also working fine.

But cant able to get value of transcationId, currency & transcationTotal in google tag manager on order completed page of our website

I have tried via javascript, html hidden field id & custom javascript as well but never worked.

My dataLayer variable is defined like this:

enter image description here

Here is dataLayer array with values in console on order completed page:

enter image description here

Getting result like this:
enter image description here

I have tried so many ways like:

  • dataLayer.currency
  • dataLayer[0].currency
  • currency
  • window.dataLayer[0].currency
  • etc

but no luck 🙁