The Ohio Class SSBN’s carry 24 Trident D-5 ICBM’s with 14 MIRV 150KT nuclear warheads each. Yikes!

I always thought it was SSBN?

SSBM = sub surface ballistic missile

No underwater, UK subs fire Tomahawk cruise missiles thru their torpedo tubes.

Cruise missiles can be launched underwater the same as a ballistic missile by a VLS vertical launch system.
With the standardisation of torpedo tubes, cruise. Missiles can also be launched this way.
The UK has Torpedo tube launch Tomahawks Cruise Missiles.

Soooo . . . a sub has to surface to launch a cruise missile?

Ballistic missiles are launched with compressed air from a submerged Sub. I believe, a cruise missile with its aerodynamic shape to facilitate navigation and lift, can not.

It is my understanding that only ballistic missiles are carried on ballistic missile boats, as their function is stealth until they have to launch.

Cruise missiles are more tactical in nature, so are carried on attack
Submarines.