Finding the Data Source

Anonymous You won't find a direct path persay, but you can go to the dataset of the report, click on the elipses "..." -> settings and look into the data source credentials area. But you would need the original file to see exactly what is being used in the dataset.

Anonymous  Still the case. Alternative thoughts. Get the credentials of the consultant user and log into Power BI as them. This assumes that they had creds in your company. Have the password reset and go explore how they set things up. Hopefully it is just a matter of adding your user to the workspace as an admin. (Hopefully they used an App workspace to share and not personal)

Alternatively, someone else should be an admin on the workspace.... I could never imagine rolling into a place and building reports without someone from the company also being an owner/admin.... Maybe check with whomever hired them.