The error message suggests that the script you're invoking has embedded \r characters, which in turn suggests that it has Windows-style \r\n line endings, instead of the Linux-style \n-only line endings that bash expects.

As a quick fix, you can remove the \r chars. as follows:

sed $'s/\r$//' input-file > output-file

This problem is mentioned in the following sources, where various solutions were suggested:

• After installing npm on WSL Ubuntu 20.04 I get the message "/usr/bin/env: ‘bash\r’: No such file or directory"
• /usr/bin/env: ‘bash\r’: No such file or directory: Incompatible line-endings (WSL?) #1725

This might be enough :

1. From WSL run sudo apt install nodejs npm to install node & npm
2. From PowerShell/CMD run wsl --shutdown to restart the WSL service
3. Next in WSL run which npm to confirm it's installed [output: /usr/bin/npm]

If this doesn't solve the issue, other solutions are suggested in the above sources.