Im struggling to see how these are presynaptic terminals/knobs and not post synaptic  , then at the end of the axon should be axon terminals and presynaptic knobs. Shouldn't the dendrites shown here have post synaptic knobs with receptors for the neurotransmitters ?

The fibers in green are axons and axon terminals **from other neurons** , not the one colored orange.

Yes, there would be post-synaptic structures associated with these but those are not drawn in this cartoon.