Hi,
WSL2 is available on Windows 10 Insider Preview Build 18917 (20H1) which is not public released and not fit for your existing system version Windows 10 1909.
So please join to insider preview or wait for public release, the time should be May 2020 as Microsoft announced last year.
Installation Instructions for WSL 2
If my information is useful for you, please take it as answer.
Bests,