I am sorry for the inconvenience, unfortunately, we can not upload a completed workout directly to Garmin connect.
You can try to export the Strava activity file and then upload it into Garmin Connect. The link below shows the instructions for manually uploading the file to Garmin Connect. However, in order to get any badges on Garmin Connect, they will need to be recorded with a Garmin watch.
https://support.garmin.com/en-US/?faq=Ht3ZP52Kju075uKvqTqu99