Polygon reduction plugin/software

Okay. Is there a plugin that can do a feature of what I would like to change the detail of 1 model to a low polygon. Here’s the example:

on the left side, You can see that the polygon counts on the curve are a total of 24 sides. and on the right side, the model has a count of 6 polygons on the curve.

There should be a tool that allows me to change the face including the lines (the curve line) to a low polygon without re-building the model again?