There are a number of tools for monitoring your position in the Google results for important search terms. We operate one for our clients free of charge. You can also look up your average position in one country or worldwide using Google Search Console, and I know many people keep a record of the results over time on a spreadsheet. However, what did the results actually look like? What competitors were there? What advertising was there? Were there ‘featured snippets’ or shopping results? If you want historic data, you’ll need to compile your own archive by taking screenshots. It’s an easy weekly or monthly task, and well worth the effort. I keep mine in a ring binder and it’s fascinating to see things change over time.
Saving a screenshot in Windows has never been as easy as it should have been, but it’s not too bad nowadays. However, a Google results page will continue well ‘below the fold’, so you really need a tool that will capture the whole thing, including everything you’d normally have to scroll down to see. There’s a great Google Chrome extension called Full Page Screen Capture which does exactly what it says, and is something I use all the time. There are add-ons for other browsers too.