I am Alexander the Great and/or a Diadochi general and I've decided to go to war against a nomadic tribe (Parthians, Saka, Scythians, Yuehzi, etc.) with my phalangites and companion cavalry. How do I fight my war? What battles exemplify these tactics?

(While I am certainly no expert in this field, I figured a response was better than no answer at all, also the first part of my answer isn't an exact answer to your question, but it provides context and answer any question you might have towards guerrilla warfare in this period).

In regards to Alexander and nomadic tribes, the best example we have is his experience in Sogdiana and Bactria, and even then it isn't a great example of outright pitched battles between a Hellenistic force versus a nomadic tribe. Alexander chased his foe Bessus into Bactria, where Bessus had been building an army of Bactrian horsemen, however this force was small in comparison to Alexanders army. With this in mind, when Alexander made it clear he had no intentions of killing the Bactrians and only wanted Bessus, the Bactrian nobles surrendered him and Alexander occupied the provinces of Bactria. However in the following months a sort of Guerrilla warfare was adopted by the Bactrians, who would allow Alexander to enter their cities, then massacre the Macedonian garrison once Alexander had left. This would result in Alexander having to retake many Bactrian forts and towns, resulting in massacres. Alongside all this, a large force of Sacae, a nomadic tribe to the north of the river Syr-Darya, had been amassing, threatening Alexanders northern border. He crossed the river with the aid of prior built ships, and gained a foothold to land his cavalry. This battle shows best what your asking for, how a Macedon force could counter Nomadic horsemen:

"There was a minor setback as the advance squadrons of mercenaries and Sarisa-equipped Macedonians were baffled and out-manoeuvred by the classic circling tactics of the nomads. Alexander adapted quickly to the challenge. He combined his cavalry and light infantry forces, using the archers and javelin men to frustrate any outflanking movements. The hit and run tactics were neutralised, and Alexander launched his own attack, an advance on a broad front by three hipparchies of Companions and the mounted javelin men and a massed charge by the rest of the cavalry, drawn up in a deep column. The details are obscure, but the result of the manoeuvre was dramatic. The Saca cavalry gave way in the face of the frontal assault and, unable to wheel and attack the Macedonian flanks, they took to flight."

So, unsurprisingly, Alexander used his cunning to counter the new tactics facing the Macedonians, and decisively defeating his enemies. Whether another Hellenistic commander could follow Alexanders footsteps in this case is a bit hard to guess, but we know there is a precedence of Hellenistic forces defeating Nomadic tribes..

Source: Conquest and Empire. The reign of Alexander the Great. A. B. Bosworth. Pg. 107 -110.