When I do not have a surname in my passport, what should I put in the?
For clarification please: your surname is your family name. Highly unusual not to have a family name and likely to cause all kinds of problems. If however, you do mean to say that you do not have a surname on your passport, then that leaves you with a first name on your passport, and that would be the one to use in any legal situation, including permanent residence applications. Good luck!