So I will first assume your router has a 2.5 or faster lan port you can connect to and also that the fiber or cable runs directly to the router/modem ?
If you can use a internal PCIE card it will likely be simpler to get good results. USB gets messy because there are so many variations and some port run at different speeds. You would need USB 3 at minimum but rather than deal with the mess of which USB port has which features I would just use a internal card.
Do not be surprised that there is almost nothing on the internet that will run that fast. Maybe the speedtest site but many other sites either can't run that fast or have artificail limitations on them to protect the servers from being overloaded by a small number of users with fast connections.