How do you say this in Turkish?>> "If you want to know, ask Ömer."

Also I want to ask, the word "istiyorum", does it mean "I want to" or just "I want"? Or can it be both?

Teşekkür ederim.

I think it is: Bilmek istiyorsan, Ömer´e sor.

istiyorum - I want

İstiyorum is very easy to join with another verb:

I want to work - Calışmak istiyorum 

In these kind of things, context makes all the difference. Namely, to know what? For example if you wanna know something about someone, "öğrenmek" would be a better option.

If you want to know if she wants to work or not, ask Ömer.

Çalışmak isteyip istemediğini öğrenmek istiyorsan Ömer´e sor.

Bilmek is certainly not wrong here, but I think "öğrenmek" is used more often in this context. Or at least that´s how I speak.

Hope it was helpful,

-Jansay

The ´to´ is not used like that in Turkish. It comes back in the suffixes and sometimes not at all.