Answer
The statement is not existential.
Informal negation: There is at least one order from store A for item B.
Formal original statement: $\forall$ orders x, if x is from store A, then x is not for item B.
Formal negation: $\exists$ an order x, such that x is from store A and x is for item B.
Work Step by Step
Recall the form of the negation of a universal conditional statement:
$~(\forall x, P(x) \rightarrow Q(x)) \equiv \exists x$ such that $(P(x) \land $ ~$Q(x))$
