Multiattack. The elemental makes two slam attacks.  Slam. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 13 (2d8 + 4) bludgeoning damage.

Whelm (Recharge 4–6).

my  questions---does it make 2 slams and a whelm or 2 attacks or a whelm or 1 attack and a whelm ?

also if it already whelmed and has targets in it, can it still make 2 slam attacks perhaps using the grappled pc as a weapon lol or is it powerless with people grappled,.

                                                                                                                                                                                                                     thanks adam

Those are two separate actions. It can either multiattack or whelm. (Or only one slam, but why would it ever do that?)

If it's already grappling, it can still act normally, since nothing in its rules or the general rules for grappled say that it can't.