The 3D model is too large for a keychain, so its size will need to be reduced before printing. 

How to Change Object Size in Ultimaker Cura

1. Open Ultimaker Cura and load your 3D model.
2. Select the object on the build plate.
3. Select the Scale tool from the left toolbar.
4. You will see the X, Y, and Z dimensions of the object.
5. To resize the object proportionally, keep Uniform Scaling enabled.
6. Enter the desired scale, for example 150% to make the object 1.5 times larger.
7. If you want to change the dimensions independently, disable the lock and adjust X, Y, or Z separately.
8. Check the model and click Slice.
9. After slicing, check the estimated print time and material usage.

Tip: If you want to increase an object's height from 20 mm to 30 mm while keeping the proportions, set the scale to 150%.