This sounds like a question that is being asked on a job application form. Essentially what the interviewer is asking is were you were previously employed by Qatar Airlines or any sister companies of Qatar Airlines?
For your reference you can find all of Qatar Airlines subsidiary companies on their website here
If you were employed with any of those companies, you would have been given an employee number on your contract of employment and probably any pay-checks you received, so this is what you will need to write on the application.
Help with filling in a job application
Need a bit of advice for the rest of your application with Qatar Airlines?
The video below has some great hints and tips to assist you when filling out a job application, plus some interview tips too! It's not for a specific job so worth a look no matter the job you are applying for.