Using Dynamic Rename to change Field

[neromerob]

Hello to everyone. 

I´m building a workflow where I must change this dynamic field 

into 2021_03; 2021_04 and so on. 

I know that i have to used a dynamic tool but I´m not sure about the code that i have to use.

Thank You . 

[TheCoffeeDude]

If all you're doing is removing "Sum_" from the values of column A, why not use the formula tool to remove it?

[TheCoffeeDude]

If you have to insist on using dynamic rename:

Here's the text of the second input file (R anchor - replacement data stream):

[Qiu · Accepted solution]

@neromerob 
@TheCoffeeDude gives good sample for using Dynamic Replace.
I noticed that you want the output to be "2021_03; 2021_04", so made minor modifications.
of course, we can use Formula tool or RegEx for this also.