.h
public:
UPROPERTY(EditAnywhere) TArray<UStaticMesh*> StaticMeshes;
.cpp, in BeginPlay
Mesh->SetStaticMesh(StaticMeshes[FMath::FRand()*StaticMeshes.Num()];
With Mesh being the UStaticMeshComponent variable that you want to change, assuming you added the static mesh component through c++.
^ May have some syntax errors as I can’t test it, but should be good.