Where can I find Conversion Action ID for Google Ads API (Upload Offline Conversion)

Question

I'm trying to send Offline Conversion with Google Ads API: 
https://developers.google.com/google-ads/api/docs/samples/upload-offline-conversion
I need conversionActionId, I know where can I find conversion id and conversion action label, but there is no info how to get conversion action id. I suppose it is something different than conversion id, because you can have multiple offline conversion for same conversion id (with different conversion label).
Do you know how to get the conversion action id?

Accepted Answer

Thank you for your answer! However ConversionActionService needs conversion action id to get info about ConversionAction so it's not useful in that case. 
Finally I solved it with query to get id by conversion action name (similar to: https://developers.google.com/google-ads/api/docs/reporting/example):
SELECT conversion_action.id FROM conversion_action WHERE conversion_action.name = 'conversion action name';
By the way, I found out that conversionActionId can be found also in Google Ads panel. When you go to conversion action details, in URL there is parameter "ctId=123456789" which represent conversion action id.