How to draw a point with more than one pixel in version 3.8.1

Hello everyone, I‘m new here. I have a question when updating an old project from XNA3.1 to Monogame.

First of all, I use GraphicsDevice.DrawUserPrimitives() to draw points, lines, etc. And in XNA3.1, I use the GraphicsDevice.RenderState.PointSize to control the pixel size of the point(usually it is 5 or 10 pixels). The question is, Monogame(and XNA4.0) does not have the class RenderState and field PointSize. So how can I realize the same effect? Thanks a lot!

According to the ChatGPT and other discussions found in the Internet, maybe create a new Texture2D object or use HLSL to write a .fx file. But as a noob, it is too difficult for me, and it does not correspond with my current code.

So what can I do? I just want to draw a point with a given pixel size.

Thanks for your time!