Code point
U+339C
Glyph appearance depends on your fonts.
U+339C
So<square> 006D 006DU+339C SQUARE MM is a Unicode 16.0.0 character in the Other Symbol category. It belongs to the CJK Compatibility block.
Choose the representation you need, then copy its value.
U+339C
13212
㎜
㎜
E3 8E 9C
339C
0000339C
%E3%8E%9C
\u339C
\u339C
\u339C
\339C