Yes, cabs are a convenient and fast way to get downtown. Depending on traffic, it usually takes about 30-40 minutes. Cab is the best option for a comfortable and fast trip. The fares at
https://aktis.taxi/Greece/Thessaloniki+Airport+Makedonia+SKG-%3EThessaloniki+City are quite reasonable. The fee will depend on the distance, but it is usually more convenient and economical than other options. Enjoy your trip and welcome to Tessaloniki!