I have 60000 similar objects (a circles formed from several points) and I want automatically convert/replace them into simple circles. The objects received from ArcGIS.
There is an effect that converts any object into an ellipse of your chosen size. Select your objects and then choose Effect > Convert to Shape > Ellipse.... You'll want to select the Absolute radio button and then key in height and width of equal measurement in order to create exact circles.
Considering the amount of shapes, you might want to create a Graphic Style. Use the above treatment on a single object, and then drag that object into the
Graphic Styles palette (Window > Graphic Styles or Shift+F5). A new miniature will be added to the palette. Now select any number of objects you want to apply the effect to and then click the miniature.
This is the result when used on a variety of shapes: