To convert $8500$ millimetres to metres, you simply divide $8500$ by $1000$, resulting in $8.5$ metres.

Let’s delve into the details of this conversion. The metric system, which is based on powers of ten, simplifies the process of converting between units. Specifically, there are $1000$ millimetres in a single metre. Therefore, when converting from millimetres to metres, the formula to use is to divide the number of millimetres by $1000$.

For instance, to convert $8500$ millimetres to metres, you can perform the following calculation:

Thus, $8500$ millimetres is equivalent to $8.5$ metres.

This conversion method applies universally to any quantity of millimetres you wish to convert. The essential step to remember is to divide by $1000$. This is rooted in the prefix ‘milli-’, which denotes one-thousandth; consequently, one millimetre is one-thousandth of a metre. By dividing by $1000$, you are effectively transitioning from the smaller unit (millimetres) to the larger unit (metres).

Grasping this conversion is not only practical in various real-world scenarios—such as measuring lengths in different units—but it is also an essential skill in GCSE Maths.