Cg is correct its a small connector that sort of looks like a cable TV wire with a small copper spike in the middle with threads inside. I don't know the name of the piece sorry. Still learning about ham radio
All the commercial radio antenna mounts I have dealt with come with no end so they can be cut to length. Motorola uses Mini UHF antenna connectors.
Try GENTLY connecting it to a cable TV fitting. If it looks like it should fit but doesn't, it is almost certainly a Mini UHF.
SMA is what is on your 396XT scanner. F is CATV connector.
YOU are the one with the antenna. You describe it as a " professional uhf magmount antenna" but give no photos or real description of the connector. You are given several answers, then ask the same question again, "What is the name?"
The name is......
Just go into a professional radio shop and say you need "FRED". If they happen to have a person named Fred, show him the antenna and ask him to give you a name.