What should be your behavior towards non Muslim parents?

You should treat them with respect, kindness, and modesty but not to follow their calling you, if any, to convert from Islam or to worship a partner with God, the one and only one God.

God says in Quran :

وَوَصَّÙÅÙ’Ùâ€Ã™Å½Ã˜Â§ الْإِÙâ€Ã˜Â³Ã™Å½Ã˜Â§Ã™â€Ã™Å½ بِوَالِدَÙÅْهِ حَمَلَتْهُ أُمُّهُ وَهْÙâ€Ã™â€¹Ã˜Â§ عَلَىٰ وَهْÙâ€Ã™Â وَفِصَالُهُ فِيعَامَÙÅÙ’Ùâ€Ã™Â Ø£ÙŽÙâ€Ã™Â اشْكُرْ لِيوَلِوَالِدَÙÅْكَ إِلَÙÅÙ‘ÙŽ الْمَصِÙÅرُ ﴿١٤﴾ وَإِنجَاهَدَاكَ عَلَىٰ أَنتُشْرِكَ بِيمَا Ù„ÙŽÙÅْسَ Ù„ÙŽÙƒÙŽ بِهِ عِلْمٌ فَلَا تُطِعْهُمَا Û– وَصَاحِبْهُمَا فِيالدُّÙâ€Ã™â€™Ã™Åَا مَعْرُوفًا Û– وَاتَّبِعْ سَبِÙÅÙ„ÙŽ Ù…ÙŽÙâ€Ã™â€™ Ø£ÙŽÙâ€Ã™Å½Ã˜Â§Ã˜Â¨Ã™Å½ إِلَÙÅÙ‘ÙŽ Ûš ثُمَّ إِلَÙÅÙ‘ÙŽ مَرْجِعُكُمْ فَأُÙâ€Ã™Å½Ã˜Â¨Ã™ÂÃ™â€˜Ã˜Â¦Ã™ÂÃ™Æ’ُم بِمَا كُÙâ€Ã˜ÂªÃ™ÂÃ™â€¦Ã™â€™ تَعْمَلُوÙâ€Ã™Å½ ﴿١٥﴾

(meaning English translation):

"And We(God-Allah) have enjoined on man (to be dutiful and good) to his parents. His mother bore him in weakness and hardship upon weakness and hardship, and his weaning is in two years give thanks to Me and to your parents, unto Me is the final destination. (14) But if they (both) strive with you to make you join in worship with Me others that of which you have no knowledge, then obey them not, but behave with them in the world kindly, and follow the path of him who turns to Me in repentance and in obedience. Then to Me will be your return, and I shall tell you what you used to do. (15)"

[Quran, chapter 31, verses 14-15]