Firefox will not ordinarily destroy your bookmarks when you uninstall it.

If you uninstall Firefox and reinstall it on the same machine without making other changes such as installing a new Operating System or specifically electing to remove personal information your bookmarks would automatically be kept and used on the new install.

The bookmarks are kept within the Firefox profile.

Please give more information about what exactly you did.

Problems with bookmarks and history not working properly can be caused by a corrupted places.sqlite database file.

You can check for problems with the places.sqlite database file in the Firefox profile folder.

• http://kb.mozillazine.org/Bookmarks_history_and_toolbar_buttons_not_working_-_Firefox
• https://support.mozilla.org/kb/Bookmarks+not+saved#w_fix-the-bookmarks-file