How to conversion
pt (point) is a unit of size mainly used in publications and is defined as “1 pt = 1/72 inch”.
dp (Density-independent pixel)
dp (density-independent pixel / dip) is a unit of size mainly used in android. 1 dp is defined as approximately equal to 1px at mdpi (160 dpi). So 1dp = 1px at mdpi and 1 dp = 2 px at xhdpi (320 dpi).
It is defined as 1 inch = 25.4 mm.
In the display, the physical size changes depending on the resolution, so it cannot be expressed in mm.