First either you accept his culture and religion beliefs.
Second option you do not accepte his culture and religion beliefs, and then you explain this to him.
He will either accept or refuse.
The understanding between a Muslim man and a Muslim woman who will get married to each other takes place at the engagement period.
An early understanding between couple is the key for long happy life.
Anita it is not necessary for you to convert to Islam and I am sure if you both get married you will be curious and ask about Islam automatically.