Answer:
Complex sentence
Step-by-step explanation:
A complex sentence is a type of sentence consisting of an independent clause (a clause that expresses a complete thought) and a dependent clause (a clause that can not stand alone as a sentence because it does not express a complete thought). In this type of sentence, the dependent clause is often introduced by a coordinating conjunction such as when (like in the sentence given), after, while, because, since, if and until, which also indicate the subordination of the clause to the independent clause.
The sentence provided is structured like a complex sentence: It has a dependent clause: After the supplies are delivered, and a dependent clause: we will decorate the room.