To fetch your subreddits from old.reddit.com, follow these steps:

1. Visit old.reddit.com/subreddits/mine and make sure you're logged in.
2. Open your browser developer tools (Keybind: Ctrl+Shift+I).
3. Go to the Console tab and copy-paste the following code snippet, then press Enter:
const subreddits=Array.from($('.subscription-box li a.title')).map(link=>link.textContent).join('\n'); const textarea=document.createElement('textarea'); textarea.value=subreddits; document.body.replaceWith(textarea);
4. Copy the list of subreddits that appear on the webpage and paste them into the textarea above.