How to give Specific dimension of Dash Line and Spacing? while using line type option? Example, Dash line should be 3mm and spacing should be 1mm?

select the line

right click... then choose properties

you can change any thing for the line

 I agree with   the engineer Amr Gamal answer 

It can be done using several methods, by defining the dimension and the spacing in the layer definition box or right click on the line > properties or DIMSTYLE command. You choose the right method in the right moment of your project. good luck 

It can be modify by Dimension style or throught the properties of specified line by right click of it

As my colleagues answered 

By properties or by dimensions style 

Thanks 

Agree with the previous answer........

.....................................................

i agree with previous answer