Some models do not have a hole, based on your needs use the function made available by BambuStudio to create the hole of the size you prefer with the following steps:

Customization:

• Scale the object appropriately for use as a Earrings.
• Adjust dimensions proportionally and control thickness independently on the Z-axis by disabling "Uniform Scale."
• To create a Earrings with a hole:
  • Select the object, right-click, choose Add Negative Part, and select Cylinder.
  • Adjust the size and position of the cylinder as needed.
• Alternatively, if you prefer not to drill the model, you can add a torus:
  • Right-click on the object, choose Add Part, and select Torus.
  • Adjust the position and size of the torus to your preference.

Adjusting Color:

• For a purer white color, scale the project in the Z-axis to at least 1.60mm while deactivating "Uniform Scale."