Wherefore (οθεν). This relatival adverb (cf. Acts 14:26; Acts 28:13) gathers up all that Paul has said.

I was not disobedient (ουκ εγενομην απειθης). Litotes again, "I did not become (second aorist middle indicative of γινομα) disobedient" (απειθης, old word already in Luke 1:17).

Unto the heavenly vision (τη ουρανιω οπτασια). A later form of οψις, from οπταζω, in LXX, and in N.T. (Luke 1:22; Luke 24:23; Acts 26:19; 2. Corinthians 12:1). Only time that Paul uses it about seeing Christ on the Damascus road, but no reflection on the reality of the event.