飛行機の手荷物のルールについてお尋ねしたいのですが・・って英語でなんて言うの？

If you 'pick someone's brains' it means that you ask them specific questions about topics which they are knowledgeable about.

This is a standard way to set up or introduce a question. It's not always necessary to use an introduction sentence like this; you could just ask the question directly or straight away.

1. You are asking about the luggage procedures.
2. You are asking about baggage rules.
3. You are asking about the amount of baggage allowed on the flight.

To 'state' something means to express an idea, fact or opinion.
Regulations and guidelines are very similar words, they both means rules, things you need to do and things that should be avoided.

inquire- investigate

"Hi, I'm not sure about my luggage, please state the luggage requirements for me?"

When travelling somewhere the bags that you take with you are called 'luggage' but they can also be called 'baggage' so you could simply say 'I have a question about baggage' but to explain clearly what you mean you could say 'I would like to ask a question about your luggage rules'

When you want to ask the airline company about the luggage rules over the phone or in person then the best to ask would be to say "Can i ask you a question regarding the luggage rules please?.