hi friends,could  any one please explain about this.my goal is lookup a column value in lookup table and only those values are allowed in my validation transform

hi i have a task to load below data for that what transform i have to useplease help me,iam the begining learner.thanks in advanceSOURCE DATA LIKE THIS...Header 1Header 2Header 3Header 4A1?10A120?B2?20B210?AND TARGET DATA SHOULD BE LIKE THIS......Hea...