CB radio aerials have a lower impedance than FM radio aerials.....50 Ohms as opposed to 75 Ohms.
However an FM radio will be alright on a CB aerial, it might not be quite as sensitive (to marginal radio stations) but it will work just fine.
There's more of an issue with CB as it's also a transmitter, so it's more important to have a matched aerial.
But again it will still work and the mismatch (SWR would probably be around 1.5 instead of the ideal 1.0)
is unlikely to make much difference.
In short, use the CB aerial and cable for your FM radio if you want....it will work!