I searched in the forum and saw the other post of the same question posted 4 years ago, tried to follow it but found I couldn't do it in 2.9.
So I created a path and converted it to mesh. Exit the Edit Mode, with the curve selected, I hit F3 to search for Simplify Curves. By applying it to the curve, it gives me an error message:Failed to find '3D Viewport: Add (Shift A) ▶ Curve ▶ Curve Simplify'
Is there a different way to do it in 2.9?