Hey there! If your car is due for inspection, you'll receive a notification letter from LTA, so if you haven't received it, I'd advise you to just wait. If it's time for inspection and you still haven't received the letter, you can just head down to an inspection centre and inform them that you didn't get the letter.

You can find out more about vehicle inspection here: https://www.motorist.sg/article/499/everything-you-need-to-know-about-vehicle-inspection-in-singapore