To show line numbers in Notepad++, put a checkmark in the checkbox labeled Display line number, as indicated by the blue arrow. If you wish to hide line numbers in Notepad++, remove the checkmark ...

To remove spaces and new lines in Notepad++, you need to use the Replace prompt. For that, go to Search and select the Replace option. Next, enter [\r\n\s]{number-of-space,} in the Find what box.