With the insights provided by the DEBUG log messages. I think I solved it.
First I got this message:
message: "Resource name \'customers/
2793184560/conversionActions/AW-338690233\' is malformed: expected \'customers/{customer_id}/conversionActions/{ConversionType.conversion_type_id}\'., at conversions[0].conversion_action"
This is the action id was wrong, it must be: like 338690322
Then I got:
message: "This customer does not have an import conversion action that matches the conversion action provided., at conversions[0].conversion_action"
So I realized I needed to create an IMPORT conversion action for Other data sources or CRM.
Now I get:
message: "This conversion action was created too recently. Please wait 4-6 hours and try uploading again., at conversions[0].conversion_action"
So I just need to wait.
I couldn't find the conversion ID first, then I found that it is in the action details page url as the query parameter &ctId=ACTION_ID
Thanks,
Rodolfo