Hello

You can get list of import fields using below steps:
Go to Sales/Products/Products
select products -> click on export
enable "I want to update data (import-compatible export)" in wizard
you will get the list of all fields that can be imported.

If you (with development mode active) go to a product (in the sales module) and start hovering over the names you will see all the fields and models.

You can also go to settings->configuration->models and look there for the models you want, as there is a list of all related fields.