How to change dimension format

This is my first question. I am very new to SD. Sorry if I haven't chosen the correct place to ask.

My question is about dimension format. When my dimension has decimal like (21.50 mm) it shows as (21/50").

How can I change the format to show dot instead of "/" and doesn't show the sign ".

It is interesting when the dimension does not have decimal (46) it shows it as 46. I tried many options in Tools/Options/ Document Option/Dimension. There are many options but I couldn't find a one for period.

Message was edited by: Asal Khoshravan Azar I added the image.

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