Your stock plan should have the data of the valuation when you signed on, and the most recent valuation. If you use something like Carta, that should all be available to you in the app. Even if you don't use an app, whomever own the stock plan should be able to give you that information.

Your compensation and retention is between you and your boss, whoever that is. You are unlikely to get good results by skipping the management chain and asking the acquirer for special treatment. But you should be able to have professional discussions with your boss about your value, and negotiate from there.

There is little chance that you can get a seat at the table for the actual acquisition. That simply isn't how acquisitions work, not unless you already hold a role where the leadership includes you in strategic discussions.

In short, talk to your boss about all your concerns.