There is no real need to know the flow rate. Just set it to be adequate for what you need done like skimming, etc.
See the article in Pool School about determining pump run time.
Jason, I thought that knowing your flow rate in GPM will help you set pump operating time such that you turn over pool water once every 24 hrs. I don't understand the "adequate for what you need..." in the reply. I have a similar pump and am struggling with the same issue. Pentair charts assume you you know your pool dynamic head, but I don't. I searched the subject on the net and got conflicting opinions for how to estimate your dynamic head.