In garmin connect do not have strava 3rd parts app I can not connect garmin to strava . 
In garmin connect do not have strava 3rd parts app I can not connect garmin to strava .
Try from the Strava web site.
Go to Strava.com > Settings > My Apps. Under social connections click "Connect with Garmin"
Log back into Garmin Connect Web and confirm Strava is connected - https://connect.garmin.com/modern/settings/accountInformation
Additionally, you'll want to confirm that you're using the same account for Garmin Connect Web as you are for Garmin Connect Mobile Android.
Go for a short test activity to see if all is well.
Go to https://www.strava.com/settings/partner_integrations
Click on "Connect with Garmin" as in this image
You don't need to do anything on the Garmin Connect Mobile app.
Yes 
I followed these steps still doesn’t work :(
In that case you need to reestablish the connection by disconnecting then reconnecting. Follow these steps. All done from the web not the phone app.
Go to Strava > Settings > My Apps - https://www.strava.com/settings/apps
Click "disconnect"
Go to Garmin Connect Web Profile > Account Settings > Account Information - https://connect.garmin.com/modern/settings/accountInformation
Click on "Disconnect," then log out of Garmin Connect Web
Go back to Strava > Settings > My Apps. Under social connections click "Connect with Garmin"
Log back into Garmin Connect Web and confirm Strava is connected - https://connect.garmin.com/modern/settings/accountInformation
Additionally, you'll want to confirm that you're using the same account for Garmin Connect Web as you are for Garmin Connect Mobile.
Go for a short test activity to see if all is well.