Key Performance Indicators (KPIs) are metrics used to quantify and measure improvement across already established processes in your business.
However, if processes are yet to be set up in your business, a good starting point to learn how to set quantifiable and qualitative goals for efficient measurement would be through OKRs: Objectives & Key Results.
The best resource on this subject is the book Measure What Matters by John Doerr: https://www.amazon.in/Measure-What-Matters-John-Doerr/dp/024134848X
