If we want to have a half model of this…
In DM, click Tools, Symmetry then select the Plane. Usually the geometry is a Full Model.
(Sometimes only one side of the part has been created before a mirror feature completes the part. In this case, then the Model Type is Partial Model.)
Generate and this is the result.
If you want the other half, you have to create a plane where the Z axis points to the half you want to keep. In this case I created Plane4.
In Mechanical, build a model and get a solution.
In Workbench, Tools, Options, Appearance, turn on Beta Options (one time configuration).
In Mechanical, click on the Symmetry item to get the details window.
Set Num Repeat to 2 and Method to Half and put 1e-3 into ∆Z.
Click on the Total Deformation and you will have the symmetry expanded.