If the libraries were actually created in FCP 10.4.10, the only way I'm aware of to work with the projects is to export them as XML from FCP 10.4.10 and then import the XML into FCP 10.4.8.
If the libraries were originally created in 10.4.8 and then updated in 10.4.10, you could go to your Final Cut Backups folder and try using a backup from prior to the update. Depends how much work was done in the library after the 10.4.10 update to know if that's a workable solution.
Best practices for professional application updates is to disable automatic updates in System Preferences and do them when you choose. When you do decide to manually update FCP, first make a zip file of the current version so you can open previous libraries without needing to update them.