‘Now after these things were ended (were fulfilled), Paul purposed in the Spirit, when he had passed through Macedonia and Achaia, to go to Jerusalem, saying, “After I have been there, it is necessary also for me to see Rome.” '
‘After these things were fulfilled' probably refers to the whole section from Acts 12:25 - Acts 19:20. He has ministered throughout Asia Minor, Macedonia and Greece. Now all that remains for him is to testify in Jerusalem and in Rome.
As suggested above ‘he purposed in the Spirit' must probably be seen as indicating the inner compulsion of the Spirit. It is by the Spirit's impulsion that he now goes forward. And this interpretation is supported by the ‘it is necessary' which regularly indicates the divine compulsion. Yet even if we took it to mean ‘purposed in (his own) spirit' our conclusion must be little different, for our knowledge of Paul is such as to recognise that he would only have this purpose if he believed it to be of God. Prior to his visit, however, it was his intention first to visit the European churches that he had founded in Macedonia and Achaia.