Can I use a 240/120 transformer and adapter cable to connect a generator to my house?
It does seem like an extra useless step. The L14-30R on the generator has two 120 V slots, a neutral slot and a ground slot. The voltage between the two 120 V slots is 240 volts. If the L14-30P on the house is wired correctly, it is connected to both 120 and 240 V circuits in the house. However the generator is not big enough to power the 240 V appliances in the house. It is not even big enough to power very many 120 V appliances. It could be that the cord that you have does not have 4 wires. It may be wired to supply only the 120 V circuits in the house that are connected to one of the two L14-30P 120V prongs. If your dad has told you to use that arrangement and you have reason to believe he has used it in the past, I would say go ahead and use it. You may find that some things in the house will not turn on. If that is the case, determine if they are things that you can live without. If they are, that is your answer.