A connection can be called fibre but that almost always refer to what is used by the ISP to connect between different points in the network, not what you get in your home.
If you need a true fibre modem/router is easy to check.
How is your current modem connected ?
If it is with a fibre cable, you will need a true fibre modem.
Normally the ISP provides the modem/router(/firewall).
If yours did, ask them to give you a new one.