You can quickly create a mirror of your design and directly save it into the new part.
To do this, preselect one of a face or plane that will be defined as the mirror plane.
Next, proceed to the pull-down menu Insert -> Mirror Part
Once the Mirror part command is clicked, a new part file will be open with the settings to be transfer into the new part on the right-side pane.
Select the information to be transferred such as solid bodies, surface bodies, and Hole Wizard data. Optionally, you may choose all of the information transferred into the new part.
While the other three settings are optional such DimXpert information, Link or break the link to the original part and copy the same appearance color as the original body on the propagate from the original part.
Once you click Ok, a mirror part will be created on the new part file as follow.