Equity = stock price x number of stocks

I have 1500 observations divided into 23 quarters. I want to estimate volatility of equity per quarter.

How can I do this? And how do I interpret my output?

arch equity, arch(1) is the command I'm using, this gives me the volatility of all my equity. How can I get it per quarter in a good way?

Any help and suggestions are very much appreciated.

Ty!