I’ve done a lot with APIs in Thunkable and I still have not been able to get a POST command to work. I know it’s possible but I find it confusing and after hours of trial and error, I usually give up.
But actually, from the link you posted above, that API looks pretty straightforward. I always get stuck when I have to create a time-stamped authentication string. But that one is just asking for two simple headers. So probably not too bad!
See this topic: Post header - SET HEADERS method
And this post in particular.