In simple terms

Column A on worksheet 1 contains 100 rows of 16 digit tag identities

Column A on worksheet 2 contains a list of 21000 rows of 16 digit tag
identites from which the 100 on sheet 1 are drawn. Column B on sheet 2 shows
a secondary unique identity for each tag.

For each tag on sheet 1 need to match and display in column C sheet 1 its
secondary ID listed in column B sheet 2