The three familiar options for incidental madd are qasr, tawassut and tul. In the traditional alif-based scale, they are described as about one, two and three alifs respectively. These are permitted alternatives for one condition: a sukun created by stopping.
When pausing on «الْعَالَمِينَ», sustain the preceding madd ya for the selected allowable duration while leaving the final nun still.
A reciter should apply the selected length in an orderly way rather than stretching one occurrence without principle and clipping another. Qasr does not mean deleting the long vowel. It still includes its correct natural duration, with no unwarranted extra extension.