Ironically, the way that you determine your WSL version number (which really is synonymous with "release" in this case) depends on the version.
The newer WSL releases, which are typically installed from the Microsoft Store as an application package, have a wsl -version command as mentioned in the comments.
From PowerShell, CMD, or from inside WSL, wsl.exe --version:
WSL version: 1.2.0.0
Kernel version: 5.15.90.1
WSLg version: 1.0.51
MSRDC version: 1.2.3770
Direct3D version: 1.608.2-61064218
DXCore version: 10.0.25131.1002-220531-1700.rs-onecore-base2-hyp
Windows version: 10.0.22621.1413
The 1.2.0.0 for me corresponds to the release on the WSL releases page you linked above. I'm currently running a pre-release version.
If wsl.exe --version simply returns help text (very likely given the older kernel that you are showing), then you are running an older release of WSL. Prior to being available as an application package, WSL was bundled in each Windows release (and still is). If you installed before 1.0.0 was available last November, then you probably have the older, legacy, in-box version. There's really no "release number" for WSL itself, since it always simply corresponded to the Windows build that it was included in. See the older WSL release notes page for examples.
If you are running an older in-box release, you can simply install WSL from the Microsoft Store to update to the latest released version (currently 1.1.3).