Hi there,
Are your bookmarks in any specific browser were deleted are in all browsers?
If this was caused by a Windows Update see if you can System Restore to a point before the problem began.
Use System Restore
https://support.microsoft.com/en-us/windows/use-system-restore-a5ae3ed9-07c4-fd56-45ee-096777ecd14e
If the bookmarks are in chrome you can check and find all the lost bookmarks back by viewing all your browsing history inside the Google Account.
Go to Google History > sign in to Google account > click History.
There, you'll be able to find all your browsing histories and then you can add them to your Chrome favorites or bookmarks again.
Below threads discusses the same issue and you can try out some troubleshooting steps from this and see if that helps you to sort the Issue.
Lost highlights and bookmarks after update https://answers.microsoft.com/en-us/windows/forum/all/lost-highlights-and-bookmarks-after-update-freda/e77e66ff-850a-42d6-b165-e755e3a14eb8
Lost Chrome Bookmarks https://answers.microsoft.com/en-us/windows/forum/all/lost-chrome-bookmarks/220fe9aa-64c9-4099-a308-dfd88550ed5b
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