You can change the dimensions proportionally regarding the size.

You can also increase or decrease the thickness by acting independently on the Z by disabling "Uniform Scale".

You can also create a keychain, adding a cylinder as a negative shape.

Enlarge the object as you wish and insert the hole for the key ring using the dedicated function!

Select the object, right click, Add Negative Part, Cylinder.

Increase or decrease the size of the cylinder and place it wherever you like!

If you don't want to drill the model you can add the torus and change the dimensions to your taste.

Right click on the object, add part, Torus.

Position and resize the object as you like!

If you want a purer white, scale the project in Z to at least 1.60mm by deactivating "Uniform Scale"