myTwist=ParametricPlot3D[{2 Cos[t],2 Sin[t], 3 t},{t,0,7}]

Now the tangent vector.  Note that I use Norm to get the length (a scalar) of the vector.  (Abs would give you a vector consisting of the absolute values of each component.)

T=D[r,t]/Norm[D[r,t]]

myT=%/.t->3 π/2

The normal unit vector....

N=D[T,t]/Norm[D[T,t]]

myN=%/.t->3 π/2

The binormal vector.  To get the cross product operator, enter esc cross esc.

myB =myT \[Cross] myN

Is this a unit vector??

Norm[myB]

r={2 Cos[t],2 Sin[t], 3 t}

%/.t-> 3π/2.0

myPoint=%

myPointsVecs=Graphics3D[{
{Green, PointSize[0.04],Point[{myPoint}]
},
{Red,
Thickness[0.005],
Arrow[{myPoint,myPoint+myT}]
},
{Blue,
Thickness[0.005],
Arrow[{myPoint,myPoint+myN}]
}
}
]

Show[myPointsVecs,myTwist]