ACoS cost for keyword - advertising



I’m just starting on Amazon FBA and I got stuck at the advertising part. I have only 1 5 stars review at the moment, but I guess I can start the PPC campaign to gain more activity for my products.

I am now reading and looking over the ACoS ( advertising cost of sales ) part.
I calculated it this way: 10.99(price on amazon)-1.2 (unit cost+transport)-5.44 (fba) = 4.39$ ( maximum price for ads per item) ; 4.39/10.99 = 39%

Ok, so what I read is that I need keywords who have ACoS less than 39% and on a website was mentioned that this value for each keyword can be seen on Amazon, but I can’t find it.

However…I think I found on a website the formula to extract the ACoS of a specific keyword. Let’s say it’s 1.2$. For a 10% margin, the formula should be: 1.2$ * 10 / 10.99 ( my sale price ), which is 109%…

That means I have to find ONLY keywords with a suggested bid price less than 0.43$ ( 0.43 * 10 / 10.99 = ~39% ) ? Or I should set the bid for a specific keyword less than 0.43$ even if the suggested bid price is ~1.2$ ?

Thank you !