So I created an update for my application (because google play devs needs to update the api....) and in the google playy console I get that this app doesnt have the api level. How can I acces to the new api? Is it ready?
Yes it is ready .
Just compile the app using nb198 to make your app compatible with SDK 34
The key change in release mb198 is upgrading the Android SDK target to 34, which aligns with Android version 14. This update is essential as it is mandatory for adding or updating apps on the Google Play Store after August 31, 2024.
so whats nb198? and how can I acces
The most recent version of version of App Inventor 2 
https://appinventor-mit-edu.ezproxy.canberra.edu.au/ai2/ReleaseNotes.html
To use SDK34 version of you app, simply re-build your app
and resubmit it to Google.
So I done it correctly and think it.
I created the file......., I upload to the google play store and it said I still have old api why? (I have 5 app and in 4 of them say that)
I don't know. Are you submitting using aab? That might be the issue.
or 4 of them use extensions that are not SDK34 compliant and one does?
or you changed the version number on some but not all?
What is different about the one app that is SDK 34 compliant from the ones that are still non compliant?
There is No problem with Target SDK
Maybe You Used a extension that it's not updated with the new google play Target SDK