How long does it take for the script to run through

if "KxFyGD" <= prefix < "L5oLmv"

The range includes all Base58 strings starting from "KxFyGD" up to (but not including) "L5oLmv". The total number of combinations is: 5852906891
If you have a script that solves one prefix in a second - 185.6 years