Nobles in 31.x work differently than before. Instead of a bunch of immigrants, your trade liaison will offer you the chance to appoint one of your own dwarves as the next baron.
This happens when you've more than 20 dwarves in total and when your dwarves have produced a certain amount of certain goods. That list eludes me by now, but I think it was something like "20 gems cut, 20 crafts/toys produced, 20 pieces of masonry made, 20 pieces of metal crafting, 20 food/drink, 20 other".
In my limited experience, the baron will still perform any tasks he had enabled when he got promoted, but his consort will from then on only sit around in their apartment and stop doing any of their previous duties. The consort didn't make any demands or mandates though.
They will get promoted to counts after some more progress or production has been made, and that happens automatically. I didn't have a fortress progressing further down that lane yet.
This means that if your civilization is dead and you've never seen a liaison or a caravan, then you won't get any nobles.
Anyway, pick out a dwarf with an agreeable set of preferences and likes and give him a name that you can keep in mind, if you think that the liaison might come up with the idea to make your fortress into a barony at some point. That's because you can't check out their preferences on the selection screen when you're asked for your recommendation.
To avoid the fact that the consort thinks that he doesn't have to work anymore, I'd also suggest that you pick a single for that promotion.