Miałbym. Chciałbym. Zjadłbym...
These longer words are used at the beginning of a sentence. And when other words are after these.
For example.
Miałbym samochód. ( I would have a car )
Chciałbym wyjść z tobą. ( I would like to go out with you )
Zjadłbym coś. ( I would eat something )
At the end of a sentence we use "bym miał", "bym chciał", "bym zjadł".
Samochód bym miał. ( I would have a car )
Z tobą wyjść bym chciał.( I would like to go out with you )
Coś bym zjadł. ( I would eat something )
But the longer forms sound better I quess. Because Poles don't say like that: Samochód bym miał or Z tobą wyjść bym chciał. It sounds weird ( maybe in poems or lyrics ).
I hope you understand. I don't know English well ( sorry ), I'm learning