* Yards measure distance: A yard is a unit of length.

* Tonnes measure weight (or mass): A tonne is a unit of weight.

To convert between these units, you need additional information:

* What material are you measuring? The weight of 10 yards will depend on the density of the material. For example, 10 yards of feathers will weigh much less than 10 yards of concrete.

* What is the shape of the material? The volume of 10 yards could be a long, thin shape or a short, wide shape. The volume will affect the weight.

Example:

Let's say you want to know the weight of 10 yards of gravel. You'll need to know the density of the gravel (usually expressed in kilograms per cubic meter). Then, you can use the following steps:

1. Convert yards to cubic meters: 1 yard = 0.9144 meters, so 10 yards = 9.144 meters. Since we need volume (cubic meters), we'll need to know the width and height of the gravel pile.

2. Calculate the volume: Volume = length x width x height.

3. Multiply volume by density: This will give you the weight in kilograms.

4. Convert kilograms to tonnes: 1 tonne = 1000 kilograms.

Let me know if you have more information about the material and its shape, and I can help you calculate the weight in tonnes.