How to use Regex/ wilcard expression on step retrieve file with conditional filename PDI (Pentaho Data Integration)

Iam a newbie using PDI 9.4 community edition,

I face little issue when trying to get data .xlsx from ftp to local with condititonal filename changed everyday from user,

So as you can see on my uploaded pict, I wish to get/retrieve excel filename with range number between 01 and 31,

for example, here it is the valid filename should be retrieve

PM 11 Desember 2023.xlsx

enter image description here

Please help and many thanks for your support.

I tried my best to retrieve filename as you can see my upload picture.

i really sorry for sort of my explanation, iam newbie here.

So if you need to match files of the type 01.xlsx to 31.xlsx, you'll need a regular expression of the type:

(0[1-9]|[1-2][0-9]|3[0-1])(\.xlsx)

You have two groups in this expression:

(0[1-9]|[1-2][0-9]|3[0-1])

and

(\.xlsx)

The first group has 3 options: 0[1-9] matches 01 to 09, [1-2][0-9] matches 10 to 29, and 3[0-1] matches 30 or 31.

The second group matches the extension .xlsx