Question:
Answer: There are many ways to orient Plate Element local axis.
1) While using mirror command - Use Reverse element local

2) In preprocessing mode we can align the plate element local axis. Goto
Node/Element main tab >
change Element parameters >
Align Element local
3) Use Plate local axis function in post-processing to check the results.
Refer our online help manual:
http://manual.midasuser.com/EN_Common/Civil/860/index.htm
4) Use UCS (User coordinate system) option to check the plate element results.

If UCS is not defined see the below screenshot to define from the UCS option