If you are upgrading from a prior version of Elements, you should convert your prior catalog and all tags will be converted. When you first launched Elements 2020, you should have been given an opportunity to convert your prior used catalog. If you failed to take that opportunity, you can still convert the catalog by going to File>Manage Catalogs and clicking the Convert button.
(The only tags that may not convert properly from a prior version are Places tags. That is because Google stopped providing their Map service and the new Map service provider names certain locations differently.)
If this is not your situation, then you need to give us more information so we can perhaps help you avoid tagging your media again.