Simply go to your campaign manager, and then you can check the CTR for each campaign, but my suggestion would be to check the CTR on the keyword level to understand the performance even better, now with the CTR in front of you, check either you got sales with high or low CTR? if you get sales with low CTR that could mean your product is being ranked either lower 1st page or top 2nd (3rd) page if you get sales with high CTR that could mean you get sales from top of search or mid 1st page, from this assess whether the click is way more than sales or not, around 1 click out of 10 must convert to a sales, so target that and optimize accordingly, though this is quite a high number and can vary from product to product.
