Create stock prices using Brownian Motion

Create stock prices Brownian Motion Im currently having an dummy firm, and want to simulate stock market using this dummy firm and firm cash value. I have a simulated firm with cash income flow and outgoing money, same with how much money a firm have. I would like to simulate stock market values of the firm, if it’s profitable it’s worth more than if it’s not. The firm have 10k stocks in total, and I would like the stock value to represents the firms buisness. Ive been told i have To USE Brownian Motion to accomplish this.