I have been to a bunch of these sorts of events- honestly the best thing to do is simply be normal and polite. If you have something you want to ask about then you should lead the convo towards that but I wouldn't shoehorn in a random careers question for the sake of it because that is going to come across as unnatural and a bit odd; you need to note that before they're a law firm partner etc. they're a person. Ask about their work for sure and try to take an interest, but I definitely wouldn't say something like "yeah I've preed your linkedin in advance of this dinner and know you did XYZ" because that's a bit scary lol💀
There are some little etiquette bits to keep in mind (handshakes, particularly for older people) but otherwise I'd say there's really nothing to be nervous about

try your best to enjoy it!