Here is the script that will allow you to backup each database within your instance of SQL Server. You will need to change the @path to the appropriate backup directory.
DECLARE @name NVARCHAR(256) -- database name
DECLARE @path NVARCHAR(512) -- path for backup files
DECLARE @fileName NVARCHAR(512) -- filename for backup
DECLARE @fileDate NVARCHAR(40) -- used for file name
-- specify database backup directory
SET @path = 'D:\OneTimeBackup\'
-- specify filename format
SELECT @fileDate = CONVERT(NVARCHAR(20),GETDATE(),112)
DECLARE db_cursor CURSOR READ_ONLY FOR
SELECT name
FROM master.sys.databases
WHERE name NOT IN ('master','model','msdb','tempdb') -- exclude these databases
AND state = 0 -- database is online
AND is_in_standby = 0 -- database is not read only for log shipping
OPEN db_cursor
FETCH NEXT FROM db_cursor INTO @name
WHILE @@FETCH_STATUS = 0
BEGIN
SET @fileName = @path + @name + '_' + @fileDate + '.bak'
BACKUP DATABASE @name TO DISK = @fileName
FETCH NEXT FROM db_cursor INTO @name
END
CLOSE db_cursor
DEALLOCATE db_cursor
