Database Backup using jenkins
I don't know of any current plugins for doing this.  That may because a lot of backup functionality is built into MSSQL.

The easiest way to automate a backup via Jenkins may be to use a command line script to use a sql command:

Sqlcmd -E -S touch -Q" BACKUP DATABASE [DBName] TO DISK = 'C:\artifact_directory\my_db_backup.BAK'

You could also also avoid automating this via Jenkins and just create a scheduled backup directly within SQL Server.