I have no interest in sex. I have no kids. We didn't have sex since long time. How to increase interest in sex so that my wife could conceive?

Lack of sex drive. I recommend couples counseling a complete urologic and blood examination. There are many causes for your symptoms.
Sexuality. I am not sure how old your wife is, whether or not she is fertile still or able to even conceive should you try. But, you ask a very powerful question. If you have no sexual feelings and want to have sexual feelings then you should explore your sexuality and your life choices in the context with a good therapist. The range of sexuality is broad. No one here can give you desire for your wife.