restore a Microsoft SQL database file

I am in the middle of switching hosting [login to view URL] company that designed my website sent me the different folders for images and pictures and also my website database [login to view URL] Database file (Microsoft SQL) was sent as a zipped backup file. I unzipped it. It is a file with the .BAK extension. I need help to restore it. The new hosting company says it is missing the MDF file and a WEBconfig file.I don't know if it is right or wrong. Anyhow, I need to know if the DB file can be restored as it is. I tried to upload the file but it gave me an error [login to view URL] let me know how to send it to you.