Export from TinkerCad into Unity
Create your object in TinkerCad.
Every different colour in your object will be a different colour and separate piece in Unity. Useful if you want to texture or animate pieces separately. Click on Export, and select OBJ file format.
This will save a ZIP file to your computer. Extract this zip file
Adjust the scale of the imported object. To exactly match the size that you created the object in TinkerCad, change the x,y,z scale from 1.0 to 0.0001. You will probably want your object to be bigger than that, so enlarge accordingly.
Change the X rotation to -90 to match the orientation in TinkerCad.