Translation:Marcus makes a long journey to the city.
That sentence might have the same general meaning, but you're paraphrasing/rewording the Latin, not translating it literally. The Latin sentence has the words "iter" (journey) and "facit" (makes), so you would need to include those exact words ("makes a journey") in your answer if you want it to be accepted.
ad (+ accusative) - to
ab/a (+ ablative) - from
A or Ab? This preposition has two forms: ab and a. Ab is used before words starting with a vowel or an H, while a is used before words starting with any other consonant.