VB6 and Object Pascal are very different languages, no matter which dialect you use.
Porting is possible. The difficult depends on the size and the complexity of the VB6 App. If it use classes and interfaces, probably it would be too hard. It woul be useful to know what kind of App you pretend to port.
I had to change all the architecture in some Apps I have ported. Practically, I have rewritten most of the code on some cases.
If it is possible, you could start porting some independent parts of the App. It will be more secure.
Anyway, you can ask some specific question of the porting. There are very helpful people here for to answer.