I used units as per ccx Table 1: Frequently used units in different unit systems. mm, N, s, K and I get stupefied with achieved heat transfer unit dimensions.

Body is a cube.

Excerpt from ccx manual “Now, since force = mass × length / time2 , we get that mass = force × time2/length. This leads to Ns2 /mm for the mass and Ns2 /mm4 for density.”

Just specifiy distances and lengths in meters.
For example in the preprocessor file for cgx, you can do simple calculations when you define values, e.g. to convert [mm] to [m]:

# Body sides
valu a1 / 10 1000
valu a2 / 10 1000
# Body depth
valu d / 3 1000
# Temperature
valu Ti + 25 273.15

A unit converter could be very useful too.
There are many out there.
I have been using Uconeer 2.4 for many years as it is super complete and free.
Not sure if you can still find it somewhere. Subsequent versions ended up being paid for.