Multiply 3 mm renal calculi? does this mean kidney stones?

Yes: Multiple 3 mm calculi are stones. Calculi = stone. They are small and you may be able to pass them without intervention (except some medication for pain). Even a 3mm stone can cause obstruction and significant pain. You should be seen by a urologist and perhaps have a stone metabolic workup to help you.

3 mm calculi: Yes, calculus is one stone; calculi are multiple stones; they are small if all are 3 mm or less; multiple 3 mm stones requires determination of cause; if not done, you require 24 hour urine testing for chemical analysis; and blood testing. Meanwhile, increase fluids to 3-4 Liters daily; add 4-5 tablespns ReaLemon Extract daily; follow low salt, low protein diet; reduce oxalate foods also;