I cant Manage to define Units

I want to define, for example mm^2

I define 'mm^2:'mm^2 or 'mm^2:'mm * 'mm and i get a Syntax Error

If I Calculate:

A:3'mm
B:5'mm
X:A*B

I get:
X=1,5*10^-5'm^2

I would like to get
X=15'mm^2

Where am I going wrong?

As an constructive Ingeneer i need even more Units as

kN/m^2 or N/mm^2

I would start out by saying that you might want to read through some of the instructions first.
There is already lots of info about how to use SMath. This is a very basic part of SMath.

For your issue specifically:

After you define X:=A*B and press enter, it will produce the default unit of m^2
You need to click on the entry and you will see a second black units box after the default m^2 one.
Click in this box and then just type in mm, press tab to insert unit, then type ^2 to make it square.




You can change the units on any result by doing the same thing as long as they are equivalent units.
Good luck.

I might add that you need to press tab to insert each unit.
So for kN/m^2, you need to type in kN, press tab, then type / and then type in m and press tab, then type in ^2 to make it square.

Thaks a lot, now i got it....press TAB some More times...