Answer:
if I finish repairing the roof (the complete adverb clause)
can go (the words it modifies)
Step-by-step explanation:
It is an adverb clause of condition because it is introduced by the conditional conjunction if. It is answering the question "Under what conditions?"
An adverb clause modifies a verb, adjective, or another adverb. The adverb clause if I finish repairing the roof modifies the verb can go.