There should be no problem with the conversion of a PSE 10 catalog to the current version. However, some creations will not transfer over, e.g. slideshow projects. You would need to export the slideshow to a video file in PSE 10, then import the video file into PSE 2021. I don't remember for sure but Elements 10 People, Events, Places tags may not transfer over to the newer system tags. I could be totally wrong about that - it's been too long since I converted an Elements 10 catalog. If you run into any issues there, we can probably find a workaround for you.
By @Greg_S.
The new tag categories replacing normal keyword categories for people, places and events were introduced in PSE11, the following version. The transfer to the new categories is automatic and based on the names of the categories. For instance, if you you have renamed your people category to 'My people', nothing will be transferred and you'll still have the old keyword hierarchy. That was my choice because I don't use face recognition. So depending on your preference, you can keep the usual 'people' keyword name or rename it to a custom new name before converting.