₪₪₪ What are the taxes and penalties for cashing out some of a 401K?

I have too much credit card debt and was considering using a portion of my 401k to pay off the cards in full. I have never done that before, and since the 401k is with my former company, I can’t take out a loan so my only option is to cash out some and roll over the rest to an IRA.

Does anyone know the taxes & penalties the IRS would charge for that, and have an opinion about whether that was a good strategy?