I'm not sure if this has been talked about before but why did mike go against his fathers morals by going into prostitution and the drugs business (this one i'm not sure about if he did or not but i'm sure knowing mike he would have to go in if the corleones had to survive or the other families would have killed them.)

Second question when Tom says they control the unions what do they mean by that the unions, trade unions?

Good questions, Zaf.
Vito initially opposed the drugs business. But as you know, he agreed to provide police and political support in order to bring Michael back from Sicily safely. So, you might argue that Michael was simply continuing his father's policy.
But it isn't clear to what extent Michael was involved with drugs after Vito died. He whacked all the Dons (including Barzini and Tattaglia, who backed Sollozzo). But we don't know if he simply folded the drugs business or (more likely, IMO) continued to protect the business and take a cut of it through Clemenza and later, Pentangeli. Frankie protests to Michael re. the Rosato brothers that "everything with them is women, broads, and a babania, junk. An' they leave the gambling to last." That statement doesn't necessarily mean that Frankie, functioning as a caporegime under Michael in NYC, had no involvement in drugs and prostitution--I take it to mean that the Rosatos were neglecting his main business--gambling. When Tom tells Michael that Frankie ratted him out to the cops, he says, "They had him on Murder One, possession.. (emphasis added). "Possession" could mean drugs--or it could mean some other illicit stuff, like guns.
To net that part out: I doubt that Michael would walk away from money-making illegal businesses in NYC.
As for the Nevada brothel that Fredo operated: Prostitution was never illegal on a statewide basis in Nevada, and Fredo's brothel was legal. Not moral, maybe, but legal. Gambling was legal, too. Since Michael intended to be "legitimate," he was in "legitimate" businesses.
As for labor unions: They are a rich source of money for organized crime in the US. They could be trade unions, craft unions and even public employee unions, but the modus operandi for the Mob is still the same. They dominate union locals by forcing their own men into leadership positions. Then they plunder unions' rich treasuries (dues, pension funds, etc.). They use unions to provide support for Mob-friendly politicians (money, voter turnout). They also extort contractors--if the contractor doesn't pay off the Mob, unions working on his site can cause a slowdown or even a strike that will cost him dearly. Unions were a very, very rich source of money and influence for Vito, and presumably, Michael. One of the reasons Vito may have had all the judges and politicians in his pocket was that the unions he controlled through his own men would steer campaign contributions and votes to them (judgeships are often elected positions in the US).

Thanks alot Turnbull everything makes sense now.

Well put TB, and I would add a few other oservations. From Frankie's comments about disliking the drug trade it would appear that the Corleones were trying to abide by the compromise Vito made to keep it away from kids and in the "dark areas."
This theme reappears in GF III in two scenes, one when two old women talk to Vincent about their neighborhood going to hell (one of them is Robert De Niro's mother in real life) and the second one in Atlantic City when Michael calls out Zasa and asks whether or not he guarantees that drugs are not being sold in the old Italian neighborhoods. Zasa dodges the question by saying he cannot guarantee that, but he can guarantee he would kill anyone he catches doing it. This tells me that Michael (who was trying to get out....sort of kind of) was no more fond of the drug business than his father.

Vincent, on the other hand, may have had a different attitude, because in GFIII when they are meeting with Dontomassino to straighten out Michael's problems, Vincent talks about the need for a strong street presence and he is openly concerned about a vacuum being created which would allow the Colombians to move in (which is exactly what happened).