Some Bibles translate this as "Why has Apis fled? Why did your bull not stand?" Apis was an Egyptian god that was represented by the form of a bull. The bull is often a symbol for strength. That is why the ULB and other versions of the Bible translate this as "strong ones" or "mighty ones," which refers to soldiers.
Yahweh uses a question to mock the strength of the Egyptian soldiers. This question can be translated as a statement. Alternate translation: "Your soldiers are face-down on the ground and will not stand" (See: [[rc://en/ta/man/translate/figs-rquestion]])