I realize the formula solution is probably not a vlookup function, but I'm
trying combinations of MATCH, SEARCH, ISNUMBER, INDEX, and still not getting
the right result.

I've got 2 worksheets.

Worksheet 1, column C has a 15-digit ID like 02i40000001fpv0.
Worksheet 2, column A has an 18-digit ID. The first 15 of the 18 are the
same as above, but + an extra 3 numbers added at the end.

I need to find the value in Worksheet 1 C2 in Worksheet column A, and return
the 18 digit value in column A.

Thanks!