How do you convert 16.8 mm to thousands?

Answer 1

16.8 mm = 0.0168 thousand mm

Unless you meant thousandths of an inch (thou):

0.0254 mm = 1 thou

→ 16.8 mm = 16.8 ÷ 0.0254 thou ≈ 661 thou

Answer 2

16800 thousand micrometres.