First, log in to your Facebook account. Then, click on the three - line menu (usually at the top - right corner on mobile or the left side on desktop). Look for 'Your Facebook Information' and click on it. Inside, there should be an option for 'Activity Log'. In the Activity Log, you can filter the content by 'Stories' to find your past ones.
Some people also find that if they regularly back up their Facebook data, they can search through the backup files for their past stories. To do this, you need to go to your Facebook settings and look for the data backup option. Download the backup and then use a file search tool to look for any files related to your stories. This is a more technical approach and might not be for everyone, but it can be useful if you want to have a complete collection of your past Facebook content.