If you talk to a person with covid for 30 minutes but the person have kn95 mask and you have a 4 ply surgical mask like 5 feet away from each other , how likely is to get covid?

Very, very, very small if negligtable chance.

There is no guarantee in this scenario but hopefully you'll be ok. Are you vaccinated? Take vitamin D and zinc. Suck on zinc lozenges. Gargle with warm salt water. Drink plenty of fluids. That person should be isolating. Call your MD for instructions but I think you should quarantine at least a week(if you get no symptoms) if you're not vaccinated.

I would think it to be highly unlikely that you would contract Covid under these circumstances, but considering that you have now had a known exposure, especially if the N95 was a valved mask, you should quarantine to be on the safe side.