You have a lot of materials in your current object, it will be much more convenient to use the *Selected to Active* bake mode:

- Duplicate your object, keep the copy at the same position as the original
- Unwrap the copy with the *Smart UV Project* mode
- Remove all the materials of the copy
- Give it a new material with an *Image Texture*, in the *Image Texture* create a new image texture that you'll call *Bake* for example
- Select the original object, shift select the copy
- In the Bake panel, choose *Bake Type > Diffuse*, disable *Constributions > Direct* and *Indirect*, enable *Selected to Active*, give a bit of *Extrusion* (0.1)
- Bake, check the result