Hi albehany, usually you would use object snaps to do that using the Transform > Move command to snap on to the center snaps. But since your target object isn't quite exactly circular (it's possibly a sweep?) there isn't a center snap available on it.

So a couple of options are you could use the BoundingBoxCenter command on the target object (http://moi3d.com/3.0/docs/moi_command_reference10.htm#boundingboxcenter) to create a point there to use as the target point in the Transform > Move command, or you could make a circle using Draw curve > Circle > Circles > 3pts snapping 3 points on to its perimeter edge to make a circle that will have a center snap to target, or also draw a line spanning across it and then use the midpoint of the line.

Please let me know if you still have problems doing any of those.

- Michael

Thank Michael,

first thank you so much I now the problem now why I can't see the center because he is not exactly circular
the shape not sweep just Boolean from box how ever I think maybe there is something wrong with it so I re model it the good news here
1- BoundingBoxCenter command work great for me
2- Circles > 3pts snapping work good I never use this tool and now I will not stop use it :)
3- draw a line spanning across it and then use the midpoint of the line not sure but this one not work for me but I am sure is my problem maybe I don't understand it however my problem is fix so thank you so much you are always have the answer for my question.