M Code for conditional column to convert inches to cm conditionally

I created a conditional column using dax programming to transform inches to centimeters. However, I must take place in Transform Column. I googled that it is M Code. Do you know how this code would look like in M Code? The intention is to create the column conditonal_column if column_a is I then col_b should be multiplied by 2.45. If it is M then do not make the multiplication.

conditional_column = IF(data[col_a] = "I", data[col_b] * 2.54, data[col_b])

This is my table

|col_a| col_b|
|-----|------|
| I   |0.4   |
| M   |0.6   |
| I   |0.12  |
| M   |0.18  |  

Expected Result

|col_a| col_b| conditional_column|
|-----|------| ------------------|
| I   |0.4   |0.10               |
| M   |0.6   |0.6                |
| I   |0.12  |0.30               |
| M   |0.18  |0.18               |

>Solution :

Add a new column and type in the following:

if [col_a] = "I" then [col_b] * 2.54 else [col_b]