Basically, we need two files to restore the database. They are .mdf and .ldf files. There is another way to restore the database, if we have the database backup file(.bak). But we can restore using one file(.mdf file) as well. Here's how it will be restored using .mdf file.
-- Restore Database using MDF File alone
EXEC sp_attach_single_file_db @dbname = 'testerDB',
@physname = 'c:\testDB.mdf'
Hope this might help.