.386
.model flat, stdcall
.data
ListaNumeros dword 1,2,3,4,5,6,7,8
.code
start:
    ;write your code here
    mov esi, OFFSET ListaNumeros
    mov ecx, LENGTHOF ListaNumeros / 2

    Ciclo:
        mov eax, [esi]
        mov ebx, [esi + 4]
        mov [esi], ebx
        mov [esi + 4], eax
        add esi, TYPE ListaNumeros * 2
    loop Ciclo
    ret
    END start