Sounds like your first task - reading the tab-delimited file -- isn't complete yet.
SAS can read these files using a couple of methods:
PROC IMPORT using DBMS=TAB, example here. Simple, but limited in flexibility.
Using DATA step with INFILE, which is probably what your teacher prefers/assumes you'll use. You get more control that way, especially if you need to adjust for data quality issues -- which sounds like some of your tasks.
You should be able to find many example of using DATA step with INFILE and tab-delimited files (DLM='09'x). Here's a SAS note on that.
You might also watch this tutorial -- it covers CSV, but the concepts are similar.
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