You might find some in your browsing history and in recently closed tabs, but sites that you haven't visited in a while will be further down. Other than that i don't know. Also keeping a lot of tabs open is gernerally not a good idea. In the future try bookmarking the sites you don't want to lose by CTRL + D, you can even add all curennt tabs in one bookmark folder using CTRL + SHIFT + D. There are also plugins you can download that back up your tabs periodically.

Also I got a folder on my desktop called "Old Firefox Data" and I messed with it and now my data in it I can't seem to find. I am really thinking I lost everything and I.. don't know what to do ;-;

Refreshing Firefox {web link} is a LAST RESORT ! !

Refreshing Firefox -- easily fix most problems

If you're having problems with Firefox, refreshing it can help. The refresh feature fixes many issues by restoring Firefox to its factory default state while saving your essential information like bookmarks and open tabs. Everything else, like user settings and add-ons, are removed. Note: Refresh saves your old profile to the desktop in a folder called Old Firefox.

Look on your desktop. Do you see a folder called; Old Firefox? Look inside. Look for the folder with the latest creation date.

https://support.mozilla.org/en-US/kb/recovering-important-data-from-an-old-profile

https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles

https://support.mozilla.org/en-US/kb/how-run-firefox-when-profile-missing-inaccessible

https://support.mozilla.org/en-US/kb/recover-user-data-missing-after-firefox-update

Yea I saw the "Old Firefox Data" folder on my desktop but I messed with it and now it's gone ;'(

Messed with it how? If you only deleted it, check in the Recycle Bin.

Like I moved it's files or made the path for the profiles be that folder and I think when I deleted the profiles on the website the folder got deleted. All I know is that I don't see it anywhere :'(

I called for more help.