A Question of Scale
'Order of magnitude' in science is a very useful concept: we are
often not necessarily interested in the exact measurement of a
quantity but rather whether it is 'about a metre' or
'about a kilometre' or 'about a nanometre' etc.
Orders of magnitude makes the use of scientific notation. For any
two numbers $X$ and $Y$ we use the notation $X$e$Y$ to mean
$X\times 10^Y$. In case you are wondering, the letter $e$ stands
for 'exponent' and is sometimes written $E$ instead. In standard
notation, the number $X$ must be between $1.0$ and $9.99...$ and
the exponent a whole number.
For example, $1.2$e$3$ is $1.2\times 10^{3}$, which is the same as
$1200$.
The power of $10$ can also be negative, so that
$6.8$e$-2$ means $6.8\times 10^{-2}$, which is the same as
$0.068$.
In science, certain exponents are more frequently used. Powers of
$\pm 3,\pm 6, \pm 9, \pm 12$ are standards, which is why you will
see (non-standard) measurements such as $375$e$-9$m, which
scientists would refer to 'Three hundred and Seventy Five
Nanometres'. You will need to convert such numbers to standard form
before placing them on the scale.
Are there any objects whose size you are confident you know? Are
the other objects larger or smaller than these?