if i buy a soundbar for my old dell monitor can i get sound from hdmi?

As the title says,I have a semi old dell monitor and it has a option for a sound bar speaker. i use this monitor mainly to play console games more then a actual monitor at the moment. I connect to the hdmi slot on the back on the monitor. I was wondering if i buy a sound bar would I be able to make it pick up the sound from the hdmi input?

Probably not. All the old sound bars (basically external speakers) I've seen require an analog audio input from the PC.
Does the monitor have a "speaker" out (usually green colored) on the monitor? If it does you can connect that to the sound bar.