How to convert slow cooker recipes to pressure cooker with different cooking times?
There is no rule, you should use the cooking times in your chart or a reputable timing chart, I use this one hippressurecooking.com/pressure-cooking-times

Basically, you'll want to phase-in the ingredients. That means, cook the beef roast for the time your cooking chart says, say 30 minutes, then open the pressure cooker and add the vegetables and pressure cooker them for their cooking time 4 minutes.

BTW, that same blog has a section where you can post a recipe and they will convert it to the pressure cooker for you. That's here: hippressurecooking.com/recipe-conversions