soft question - How to correctly show units with a vector

Supposed I have an position vector $$\vec{r}=\begin{pmatrix} 10.0 & -30.0 & 25.0\end{pmatrix}$$ expressed in $\mathrm{millimeters}$.

What is the correct notation to display $\vec{r}$

1. $\begin{pmatrix} 10.0 & -30.0 & 25.0\end{pmatrix}\text{ mm}$


2. $\begin{pmatrix} 10.0\text{ mm} & -30.0\text{ mm} & 25.0\text{ mm}\end{pmatrix}$


3. $\begin{pmatrix} 10.0 & -30.0 & 25.0\end{pmatrix}\text{ in }\mathrm{mm}$

If the answer is 2. then why add all those redundunt units when all elements of a vector have to be of the same unit. If you have a long list of values then usualy you present this a table with the units in the header (and not on each element). What if the units are complex (with powers and fraction), do we really have to write them out for each element?

How would you consicely write out a vector while describing the units those values are in also at the same time?

PS. I did not post this in the Math SE because they have never heard of units :-) and only physics deals with real situations.

Answer

I would say 1. and 2. are correct. In the first you are multiplying by the scalar 1 mm.
Also elements of vectors dont need to have the same units.
Just consider the 4-vector (3 sec, 1 µm, 82 ly, 5.6 parsec)