I have 2011 Toyota Sienna LE V6 minivan. The van is reaching 100,000 miles. I want to know should I still use 0W-20 oil for the engine or do I need to change the weigh of the oil because the vehicle has high miles.

I would use SAE 5W-20 full synthetic engine oil, which is recommended by Toyota.

Yes, continue using 0w-20 or 5w-20, but be sure it's full synthetic. Keep doing that and you'll see 200,000, 300,000, before you know it by the way you treat that taxi. :)