How to find the volume of a stock on the stock market?

The volume of an action (ie how much is sold) is reported daily in almost every website (like Yahoo Finance), which has sections for financial information. You can also find the number of shares was issued from the same view.

The volume is generally irrelevant to the company

(unless the company is planning to issue new shares or repurchase shares of age), but should be a factor when deciding to buy shares. Stock low volume can be relatively illiquid, which means it's harder to sell and are more likely to incur costs (the spread) by having to use a market maker.