I think we’ve given enough things for the original poster to try to get around their problem, so they can continue to paste from Notepad++ through something else into Teams.

At this point, if the OP has any more questions on other things to try, they should really go to a forum dedicated to Team or MS products or general computing.
(In case my original statements weren’t clear, when I said “the issue is not a problem with Notepad++” and “we are not a Teams support forum”, that was supposed to be interpreted as "and thus, any further Teams-specific followon does not belong in this forum, as it is off topic.)

Are we teaching Teams and markdown here?

I am not a Microsoft Teams user, though a search provides some clues of formatting.

Use Markdown formatting in Teams

Try 3 backticks on 1st line and 3 backticks on last line.

```
13/04/2022

Resource1
    Country1
        Work Item1
```

or try unordered list with asterisks.

13/04/2022

Resource1

 * Country1
   * Work Item1

That might copy from Notepad++ to Microsoft Teams and view a bit better.

The same thing happens when I paste from Microsoft Notepad into Microsoft Teams. Thus, the issue is not a problem with Notepad++ as the source of the copy/paste, the issue is with teams as the receiver of the copy/paste.

We are not a Teams support forum, so we cannot help you solve the actual problem, because it’s that Teams doesn’t honor spaces in plain-text copy/paste.

However, as a workaround: if you have Teams, you might also have MS Word. If so, copy the indented text from Notepad++ and paste into Word. Then re-copy from Word (doing a new Ctrl+C from Word is important, because it changes the copy buffer) and paste into Teams. Now it will preserve the formatting, because Word puts other formats into the clipboard, with Microsoft-specific encoding, and Teams uses one of those Microsoft-specific clipboard contents to put into Teams. (No, Notepad++ does not and will not populate non-plaintext items in the clipboard, because Notepad++ is a text editor, not a word processor).

Notepad++ can’t control what Teams does with data you paste into it.

Bottom line: Notepad++ is handing Windows clipboard the data with spaces intact. Windows is giving Teams the data with the spaces intact, and Teams is doing what it wants with it.