Lost all Safari iPad tabs after window was unintentionally closed?

After closing out my open windows the other day (like I have regularly done since getting my iPad in 2019), I went back to Safari and noticed that all my tabs were gone. I have had 4 years worth of tabs open on there and they're just all gone??? What can I do to get them back??? I had really important and niche tabs open that I couldn't possibly hope to find all over again. I can't even find a 'reopen closed windows' button anywhere to try and troubleshoot this. The second picture is the only thing that pops up when I press 'show all windows'.