Honestly, there's no legal and reliable way within Instagram itself to download old stories. Trying to use unauthorized methods can lead to serious consequences for your account.
You can find ways to download Instagram stories, but be cautious. Instagram doesn't officially support it, and doing so could have consequences for your account and privacy.
You could potentially find ways to download them, but it's against Instagram's policies. This could lead to negative consequences for your account and it's not ethical to do so without proper authorization.
There are a few methods. One way is to look for screen recording apps on your phone and record the stories while they play. Another option is to search for specific Instagram story downloader apps, but make sure they are reliable and legal.
You can try using Instagram's built-in archive feature. Just go to your settings and look for the archive option. It might allow you to download your old stories.