Retrieve data of a row in the table

I have a table with 2 columns as follows:

pos column consists of integers from 1 -> n,

iwant column contains permutations of string 012345

How can I get a pos when I know iwant?

desired results: iwant = '542031' ---> pos = 11

Help me! Thank you very much!

[hang dong]

What is the error when running the results below?

Answer 1

[J. Alex Lee]

You could do

T.pos(T.iwant==542031)