Explanation:

- A metre is a standard unit of length in the metric system.

- A micron, or micrometre, is one millionth of a metre.

- To convert metres to microns, multiply by 1,000,000.

- Therefore, 1 metre equals 1,000,000 microns.

- Options analysis:

- Option 1: 1,000 - This converts millimetres to microns.

- Option 2: 10,000 - This applies to centimetres to microns.

- Option 3: 1,000,000 - This is correct for metres to microns.

- Option 4: 100,000 - Represents decimetres to microns.