Garmin connect is a great place to collect all of your fitness data together from your weight to calories burnt etc.
Recently I was asked if I could get the weight at a out of the site for use in EXCEL so I had a little dig around and found the following:
Once you are logged into the Garmin Connect portal you can then copy/paste this URL into your browser bar hit return and you’ll see the data.
Copy and paste the WHOLE document or save it to your hard drive and then head to https://json-csv.com/ where you can convert that data to a CSV for use in Excel etc
To edit the start and end dates you will need to use the website https://www.epochconverter.com/ and replace the numbers in from=[FROM EPOCH] and until=[TO EPOCH]